The Third National Health and Nutrition Examination Survey (NHANES III),
1988-94, Series 11, No. 8A Data Release.
The National Center for Health Statistics (NCHS) of the Centers for Disease
Control and Prevention (CDC) collects, analyzes, and disseminates data on the
health status of U.S. residents. The results of surveys, analyses, and studies
are made known through a number of data release mechanisms including
publications, mainframe computer data files, CD-ROMs (Search and Retrieval
Software, Statistical Export and Tabulation System (SETS)), and the Internet.
The National Health and Nutrition Examination Survey (NHANES) is a periodic
survey conducted by NCHS. The third National Health and Nutrition Examination
Survey (NHANES III), conducted from 1988 through 1994, was the seventh in a
series of these surveys based on a complex, multi-stage sample plan. It was
designed to provide national estimates of the health and nutritional status of
the United States' civilian, noninstitutionalized population aged two months
and older.
This data release, Series 11 No. 8A, includes NHANES data and data prepared
by the Division of Vital Statistics, NCHS. Since 1985, natality statistics for
all States, the District of Columbia, U.S. Virgin Islands, Puerto Rico, and
Guam have been based on information from the total file of birth records. The
information is received on computer data tapes coded by the States and provided
to NCHS through the Vital Statistics Cooperative Program.
Series 11 No. 8A includes Natality data for births occurring within the United
States to residents and nonresidents. Of the 8,836 children 2 months through 6
years of age from whom interview data were obtained in NHANES III, 7779 have
linked birth certificates from the NCHS Division of Vital Statistics. Births
occurring to US citizens outside the US are not included in this file. This
data release does not replace the previous NHANES III data release.
Background information on the procedures, survey components, questionnaires,
examination and laboratory methods, and statistical analysis guidelines is
available on the NHANES III Reference Manuals and Reports (CD-ROM). All data
users are strongly encouraged to review these reference materials and reports
before analyzing NHANES III data.
Guidelines for Data Users
o NHANES III survey design and demographic variables are found on the
Household Adult Data File, Household Youth Data File, the Laboratory
Data File and the Examination Data File. In preparing a data set
for analysis, other data files should be merged with either or both
of the Adult Household Data File or the Youth Household Data File
to obtain many important analytic variables.
o All of the NHANES III public use data files are linked with the common
survey participant identification number (SEQN). Merging information
from multiple NHANES III data files using this variable ensures that
the appropriate information for each survey participant is linked
correctly.
o NHANES III public use data files do not have the same number of records
on each file. The Household Questionnaire Files (divided into two files,
Adult and Youth) contain more records than the Examination Data File
because not everyone who was interviewed completed the examination. The
Laboratory Data File contains data only for persons aged one year and
older. The Individual Foods Data File based on the dietary recall, the
Prescription Medication Data File, and The Vitamin and Minerals Data File
all have multiple records for each person rather than the one record per
sample person contained in the other data files.
o For each data file, SAS program code with standard variable names and
labels is provided as separate text files on the CD-ROM that contains the
data files. This SAS program code can be used to create a SAS data set
from the data file.
o Modifications were made to items in the questionnaires, laboratory, and
examination components over the course of the survey; as a result, data
may not be available for certain variables for the full six years. In
addition, variables may differ by phase since some changes were
implemented between phases. Users are encouraged to read the Notes
sections of the file documentation carefully for information about
changes.
o Extremely high and low values have been verified whenever possible, and
numerous consistency checks have been performed. Nonetheless, users
should examine the range and frequency of values before analyzing data.
o Some data were not ready for release at the time of this publication
due to continued processing of the data or analysis of laboratory
specimens. A listing of those data are available in the general
information section of each data file.
o Confidential and administrative data are not available or released to the
public. Additionally, some variables have been recoded to protect the
confidentiality of the survey participants. For example, all age-related
variables were recoded to 90+ years for persons who were 90 years of age
or older.
o Some variable names may differ from those used in the Phase 1
NHANES III Provisional Data Release and some variables included in the
Phase 1 provisional release may not appear on these files. Do not use
the Phase 1 provisional release; use the current (six-year) release.
o Although the data files have been edited carefully, it is possible that
errors may still exist. Please notify NCHS staff (301-458-4636) of any
suspected errors in the data file or the documentation. Refer to the
NCHS website at http://www.cdc.gov/nchs/nhanes.htm for updates to these
data files.
Analytic Considerations
o NHANES III (1988-94) was designed so that the survey's first three years,
1988-91, its last three years, 1991-94, and the entire six years were
national probability samples. Analysts are encouraged to use all six
years of survey results.
o Sample weights are available for analyzing NHANES III data. One of the
following three sample weights will be appropriate for nearly all
analyses: interviewed sample final weight (WTPFQX6), examined sample
final weight (WTPFEX6), and mobile examination center (MEC)- and
home-examined sample final weight (WTPFHX6). Choosing which of these
sample weights to use in any analysis depends on the variables being
used. A good rule of thumb is to use "the least common denominator"
approach. In this approach, the user checks the variables of
interest. The variable that was collected on the smallest number of
persons is the "least common denominator," and the sample weight that
applies to that variable is the appropriate one to use for that
analysis. For more detailed information, see the Analytic and
Reporting Guidelines for NHANES III (U.S. DHHS, 1996).
Referencing or Citing NHANES III Data
o In publications, please acknowledge NCHS as the original data source.
For instance, the reference for the NHANES III Examination Data File on
this release: U.S. Department of Health and Human Services (DHHS).
National Center for Health Statistics. Third National Health and
Nutrition Examination Survey, 1988-1994, NHANES III Natality Data File
(Series 11, No. 8A). Hyattsville, MD: Centers for Disease Control
and Prevention, 1999.
Using the files from this Data Release
Your analysis software should be able to read data files from this release after
the extraction from the "zipped" file named Natal.EXE. In order to extract the
data files, documentation and SAS code please follow these steps:
o Copy this file to an appropriate directory or folder on your hard-drive.
o If you are using a PC compatible computer, double-click on the file from
within Windows Explorer (not Internet Explorer). This will extract all of
the necessary files into the directory or folder you have chosen. The
documentation files is named natal.doc. The SAS programs to convert
the flat files into SAS format are named natal.SAS. The ASCII data files
is named natal.DAT.
To access a documentation file open it in a word processor, set the margins
to zero and the font to Courier 12 point. View or print any pages needed.
Some of these documents are hundreds of pages long.
For SAS users, open the SAS program for the data set required into Program
Manager. Change the FILENAME statement as needed for the operating system
(the supplied FILENAME assumes DOS conventions where the hard-drive is C:\).
To create a permanent SAS data set, modify your data step statement as required
by your operating system. If space is limited, consider adding a KEEP statement
to specify the variables of interest.
The data files may be used in other analysis packages by using the field
positions found in the index portion of the corresponding documentation.
Problems Using the Data
NHANES III is a wonderfully rich source of data and NCHS encourages you to use
the data for research and analysis. However, the dataset is large and complex
and familiarity with data file manipulation and analysis is required. NCHS does
not have the personnel resources to perform analyses, check results, debug
programs or do literature review for your work. Thorough review of the
extensive documentation on the planning of the survey, analytic guidelines and
individual datasets should resolve most questions. If you still have questions
after careful review of the documentation, please contact the Data Dissemination
Branch at (301)458-4636.
NHANES III Examination Data File Index
------------------------------------------------------------------------
Variable
Description Name Positions
------------------------------------------------------------------------
GENERAL INFORMATION
Sample Person identification number ......... SEQN 1-5
Family sequence number ...................... DMPFSEQ 6-10
Examination/interview status ................ DMPSTAT 11
Race-ethnicity .............................. DMARETHN 12
Race ........................................ DMARACER 13
Ethnicity ................................... DMAETHNR 14
Sex ......................................... HSSEX 15
Date of screener: month ..................... HSDOIMO 16-17
Age at interview (screener) - qty ........... HSAGEIR 18-19
Age at interview (screener) - unit .......... HSAGEU 20
Age in months at interview (screener) ....... HSAITMOR 21-24
Age at exam - in days ....................... MXPAXTDR 25-28
Family size (persons in family) ............. HSFSIZER 29-30
Household size (persons in dwelling) ........ HSHSIZER 31-32
Rural/urban code based on USDA code ......... DMPMETRO 33
Census region ............................... DMPCREGN 34
Poverty Income Ratio (unimputed income) ..... DMPPIR 35-40
Phase of NHANES III Survey .................. SDPPHASE 41
Total NHANES III pseudo-PSU ................. SDPPSU6 42
Total NHANES III pseudo-stratum ............. SDPSTRA6 43-44
Pseudo-PSU for phase 1 ...................... SDPPSU1 45
Pseudo-stratum for phase 1 .................. SDPSTRA1 46-47
Pseudo-PSU for phase 2 ...................... SDPPSU2 48
Pseudo-stratum for phase 2 .................. SDPSTRA2 49-50
Total interviewed sample final weight ....... WTPFQX6 51-58
Total MEC examined sample final weight ...... WTPFEX6 59-66
Total M+H examined sample final weight ...... WTPFHX6 67-74
Total allergy subsample final weight ........ WTPFALG6 75-82
Phase 1 interviewed sample final wgt ........ WTPFQX1 83-91
Phase 1 MEC examined sample final wgt ....... WTPFEX1 92-100
Phase 1 M+H examined sample final wgt ....... WTPFHX1 101-109
Phase 1 allergy subsample final wgt ......... WTPFALG1 110-118
Phase 2 interviewed sample final wgt ........ WTPFQX2 119-127
Phase 2 M+H examined sample final wgt ....... WTPFHX2 128-136
Phase 2 MEC examined sample final wgt ....... WTPFEX2 137-145
Phase 2 allergy subsample final wgt ......... WTPFALG2 146-154
Replicate 1 final interview weight .......... WTPQRP1 155-162
Replicate 2 final interview weight .......... WTPQRP2 163-170
Replicate 3 final interview weight .......... WTPQRP3 171-178
Replicate 4 final interview weight .......... WTPQRP4 179-186
Replicate 5 final interview weight .......... WTPQRP5 187-194
Replicate 6 final interview weight .......... WTPQRP6 195-202
Replicate 7 final interview weight .......... WTPQRP7 203-210
Replicate 8 final interview weight .......... WTPQRP8 211-218
Replicate 9 final interview weight .......... WTPQRP9 219-226
Replicate 10 final interview weight ......... WTPQRP10 227-234
Replicate 11 final interview weight ......... WTPQRP11 235-242
Replicate 12 final interview weight ......... WTPQRP12 243-250
Replicate 13 final interview weight ......... WTPQRP13 251-258
Replicate 14 final interview weight ......... WTPQRP14 259-266
Replicate 15 final interview weight ......... WTPQRP15 267-274
Replicate 16 final interview weight ......... WTPQRP16 275-282
Replicate 17 final interview weight ......... WTPQRP17 283-290
Replicate 18 final interview weight ......... WTPQRP18 291-298
Replicate 19 final interview weight ......... WTPQRP19 299-306
Replicate 20 final interview weight ......... WTPQRP20 307-314
Replicate 21 final interview weight ......... WTPQRP21 315-322
Replicate 22 final interview weight ......... WTPQRP22 323-330
Replicate 23 final interview weight ......... WTPQRP23 331-338
Replicate 24 final interview weight ......... WTPQRP24 339-346
Replicate 25 final interview weight ......... WTPQRP25 347-354
Replicate 26 final interview weight ......... WTPQRP26 355-362
Replicate 27 final interview weight ......... WTPQRP27 363-370
Replicate 28 final interview weight ......... WTPQRP28 371-378
Replicate 29 final interview weight ......... WTPQRP29 379-386
Replicate 30 final interview weight ......... WTPQRP30 387-394
Replicate 31 final interview weight ......... WTPQRP31 395-402
Replicate 32 final interview weight ......... WTPQRP32 403-410
Replicate 33 final interview weight ......... WTPQRP33 411-418
Replicate 34 final interview weight ......... WTPQRP34 419-426
Replicate 35 final interview weight ......... WTPQRP35 427-434
Replicate 36 final interview weight ......... WTPQRP36 435-442
Replicate 37 final interview weight ......... WTPQRP37 443-450
Replicate 38 final interview weight ......... WTPQRP38 451-458
Replicate 39 final interview weight ......... WTPQRP39 459-466
Replicate 40 final interview weight ......... WTPQRP40 467-474
Replicate 41 final interview weight ......... WTPQRP41 475-482
Replicate 42 final interview weight ......... WTPQRP42 483-490
Replicate 43 final interview weight ......... WTPQRP43 491-498
Replicate 44 final interview weight ......... WTPQRP44 499-506
Replicate 45 final interview weight ......... WTPQRP45 507-514
Replicate 46 final interview weight ......... WTPQRP46 515-522
Replicate 47 final interview weight ......... WTPQRP47 523-530
Replicate 48 final interview weight ......... WTPQRP48 531-538
Replicate 49 final interview weight ......... WTPQRP49 539-546
Replicate 50 final interview weight ......... WTPQRP50 547-554
Replicate 51 final interview weight ......... WTPQRP51 555-562
Replicate 52 final interview weight ......... WTPQRP52 563-570
Replicate 1 final exam weight ............... WTPXRP1 571-578
Replicate 2 final exam weight ............... WTPXRP2 579-586
Replicate 3 final exam weight ............... WTPXRP3 587-594
Replicate 4 final exam weight ............... WTPXRP4 595-602
Replicate 5 final exam weight ............... WTPXRP5 603-610
Replicate 6 final exam weight ............... WTPXRP6 611-618
Replicate 7 final exam weight ............... WTPXRP7 619-626
Replicate 8 final exam weight ............... WTPXRP8 627-634
Replicate 9 final exam weight ............... WTPXRP9 635-642
Replicate 10 final exam weight .............. WTPXRP10 643-650
Replicate 11 final exam weight .............. WTPXRP11 651-658
Replicate 12 final exam weight .............. WTPXRP12 659-666
Replicate 13 final exam weight .............. WTPXRP13 667-674
Replicate 14 final exam weight .............. WTPXRP14 675-682
Replicate 15 final exam weight .............. WTPXRP15 683-690
Replicate 16 final exam weight .............. WTPXRP16 691-698
Replicate 17 final exam weight .............. WTPXRP17 699-706
Replicate 18 final exam weight .............. WTPXRP18 707-714
Replicate 19 final exam weight .............. WTPXRP19 715-722
Replicate 20 final exam weight .............. WTPXRP20 723-730
Replicate 21 final exam weight .............. WTPXRP21 731-738
Replicate 22 final exam weight .............. WTPXRP22 739-746
Replicate 23 final exam weight .............. WTPXRP23 747-754
Replicate 24 final exam weight .............. WTPXRP24 755-762
Replicate 25 final exam weight .............. WTPXRP25 763-770
Replicate 26 final exam weight .............. WTPXRP26 771-778
Replicate 27 final exam weight .............. WTPXRP27 779-786
Replicate 28 final exam weight .............. WTPXRP28 787-794
Replicate 29 final exam weight .............. WTPXRP29 795-802
Replicate 30 final exam weight .............. WTPXRP30 803-810
Replicate 31 final exam weight .............. WTPXRP31 811-818
Replicate 32 final exam weight .............. WTPXRP32 819-826
Replicate 33 final exam weight .............. WTPXRP33 827-834
Replicate 34 final exam weight .............. WTPXRP34 835-842
Replicate 35 final exam weight .............. WTPXRP35 843-850
Replicate 36 final exam weight .............. WTPXRP36 851-858
Replicate 37 final exam weight .............. WTPXRP37 859-866
Replicate 38 final exam weight .............. WTPXRP38 867-874
Replicate 39 final exam weight .............. WTPXRP39 875-882
Replicate 40 final exam weight .............. WTPXRP40 883-890
Replicate 41 final exam weight .............. WTPXRP41 891-898
Replicate 42 final exam weight .............. WTPXRP42 899-906
Replicate 43 final exam weight .............. WTPXRP43 907-914
Replicate 44 final exam weight .............. WTPXRP44 915-922
Replicate 45 final exam weight .............. WTPXRP45 923-930
Replicate 46 final exam weight .............. WTPXRP46 931-938
Replicate 47 final exam weight .............. WTPXRP47 939-946
Replicate 48 final exam weight .............. WTPXRP48 947-954
Replicate 49 final exam weight .............. WTPXRP49 955-962
Replicate 50 final exam weight .............. WTPXRP50 963-970
Replicate 51 final exam weight .............. WTPXRP51 971-978
Replicate 52 final exam weight .............. WTPXRP52 979-986
Certificate availability status ............. NTCERT 987
Record type ................................. NTRECTYP 988
Resident status recode ...................... NTRSTATR 989
Record weight ............................... NTRECWT 990
Place or facility of birth .................. NTPLDEL 991-992
Attendant at birth .......................... NTBIRATT 993
Metropolitan - nonmetropolitan recode ....... NTMETROR 994
Reported age of mother used flag ............ NTMAGEFL 995
Age of mother imputation flag ............... NTMAGEIM 996
Age of mother recode ........................ NTMAGER 997-998
Hispanic origin of mother recode ............ NTMETHNR 999
Race of mother imputation flag .............. NTMRACIM 1000
Race of mother .............................. NTMRACE 1001
Education of mother recode .................. NTMEDUCR 1002-1003
Marital status of mother imputation flg ..... NTMSTIMP 1004
Marital Status of mother .................... NTMMRST 1005
Place of birth of mother recode ............. NTMPOBR 1006
Adequacy of care recode (Kessner index) ..... NTADEQUA 1007
Number of previous live births-living ....... NTNLBNLR 1008-1009
Number of previous live births-dead ......... NTNLBNDR 1010
Interval since last live birth recode ....... NTISLLBR 1011-1013
Number of other terminations recode ......... NTTERMR 1014
Interv. months since last other term. ....... NTISLTR 1015-1017
Interv. between deliveries recode ........... NTINDLVR 1018-1020
Outcome of last pregnancy ................... NTOUTCOM 1021
Interpregnancy interval - in months ......... NTINTPGR 1022-1024
Live birth order recode ..................... NTLBOR 1025-1026
Total birth order recode .................... NTTBOR 1027-1028
Month pregnancy prenatal care began ......... NTMONPRE 1029-1030
Number of prenatal visits recode ............ NTTNPVR 1031-1032
Reported age of father used flag ............ NTFAGEFL 1033
Age of father recode ........................ NTFAGER 1034-1036
Hispanic origin of father recode ............ NTFETHNR 1037
Race of father .............................. NTFRACE 1038
Education of father recode .................. NTFEDUCR 1039-1040
Clinical estimate of gestation used ......... NTGESTFL 1041
Gestation imputation flag ................... NTGESTIM 1042
Period of gestation recode .................. NTGESTR 1043-1045
Sex imputation flag ......................... NTSEXIMP 1046
Sex ......................................... NTSEX 1047
Race of child ............................... NTCRACE 1048
Birth weight recode - in grams .............. NTBWTR 1049-1052
Plurality imputation flag ................... NTPLUIMP 1053
Plurality recode ............................ NTPLURR 1054
One minute Apgar score recode ............... NTOMAPSR 1055-1056
Five minute Apgar score recode .............. NTFMAPSR 1057-1058
Clinical estimate of gestation recode ....... NTCGESTR 1059-1060
Vaginal ..................................... NTVAGINA 1061
Vaginal birth after previous C-section ...... NTVBAC 1062
Primary C-section ........................... NTPRIMAC 1063
Repeat C-section ............................ NTREPEAC 1064
Vaginal or C-section recode ................. NTDELIVR 1065
Forceps ..................................... NTFORCEP 1066
Vacuum ...................................... NTVACUUM 1067
Anemia recode ............................... NTAORHR 1068
Cardiac disease ............................. NTCARDIA 1069
Acute or chronic lung disease ............... NTLUNG 1070
Diabetes .................................... NTDIABET 1071
Genital herpes .............................. NTHERPES 1072
Hydramnios/Olighydramnios ................... NTHYDRA 1073
Hypertension, chronic ....................... NTCHYPER 1074
Hypertension, pregnancy-associated .......... NTPHYPER 1075
Eclampsia ................................... NTECLAMP 1076
Incompetent cervix .......................... NTINCERV 1077
Previous infant 4000+ grams ................. NTPR4000 1078
Previous preterm or small-for-gestation ..... NTPRTERM 1079
Renal disease ............................... NTRENAL 1080
Rh sensitization ............................ NTRH 1081
Uterine bleeding ............................ NTUTERIN 1082
Other medical risk factors .................. NTOTHRMR 1083
Tobacco use during pregnancy recode ......... NTTOBACR 1084
Avg. number of cigarettes per day rec. ...... NTCIGARR 1085-1086
Alcohol use during pregnancy recode ......... NTALCOHR 1087
Average number of drinks per week recode .... NTDRINKR 1088
Weight gain recode .......................... NTWTGNR 1089-1090
Amniocentesis ............................... NTAMNIO 1091
Electronic fetal monitoring ................. NTMONITO 1092
Induction of labor .......................... NTINDUCT 1093
Stimulation of labor ........................ NTSTIMUL 1094
Tocolysis ................................... NTTOCOL 1095
Ultrasound .................................. NTULTRAS 1096
Other obstetric procedures .................. NTOTHROB 1097
Febrile ..................................... NTFEBRIL 1098
Meconium, moderate/heavy .................... NTMECONI 1099
Premature rupture of membrane ............... NTRUPTUR 1100
Abruptio placenta ........................... NTABRUPT 1101
Placenta previa ............................. NTREPLAC 1102
Other excessive bleeding .................... NTEXCBLD 1103
Seizures during labor ....................... NTSEIZUR 1104
Precipitous labor (<3 hours) ................ NTPRECIP 1105
Prolonged labor (>20 hours) ................. NTPRLONG 1106
Dysfunctional labor ......................... NTDYSFUN 1107
Breech/malpresentation ...................... NTBREECH 1108
Cephalopelvic disproportion ................. NTCEPHAL 1109
Cord prolapse ............................... NTCORD 1110
Anesthetic complications .................... NTANESTH 1111
Fetal distress .............................. NTDISTRE 1112
Other complications of labor ................ NTOTHRLB 1113
Anemia (Hct.<39/Hgb.<13) .................... NTNANEMI 1114
Birth injury ................................ NTINJURY 1115
Fetal alcohol syndrome ...................... NTALCOSY 1116
Hyaline membrane disease .................... NTHYALIN 1117
Meconium aspiration syndrome ................ NTMECONS 1118
Assisted ventilation, < 30 minutes .......... NTVENL30 1119
Assisted 30+ minutes ........................ NTVEN30M 1120
Other abnormal conditions recode ............ NTOTHABR 1121
Other circulatory/respiratory anomalies ..... NTCIRCUL 1122
Club foot ................................... NTCLUBFT 1123
Othr musculoskeletal/integumental anom. ..... NTMUSCUL 1124
Major congenital anomalies recode ........... NTCONMJR 1125
Minor congenital anomalies recode ........... NTCONMNR 1126
Marital status (by state) ................... NTFLMSST 1127
Education of parents (by state) ............. NTFLEPST 1128
Education of mother ......................... NTFLEDM 1129
Education of father ......................... NTFLEDF 1130
Date of last menses (by state) .............. NTFLNMST 1131
Date of last live birth (by state) .......... NTFLLBST 1132
Date of last other termination by state ..... NTFLLTST 1133
Number of prenatal visits (by state) ........ NTFLPVST 1134
One minute Apgar score (by state) ........... NTFL1APS 1135
Five minute Apgar score (by state) .......... NTFL5APS 1136
Clinical estimate of gestation .............. NTFLGEST 1137
Tobacco use ................................. NTFLTOBU 1138
Alcohol use ................................. NTFLALCU 1139
Weight gain ................................. NTFLWTGN 1140
Congential anomalies ........................ NTFLCONG 1141
GENERAL NOTES
Many variables on this data file were recoded to protect confidentiality. The
minimum or maximum categories were collapsed in order to prevent potential
identification of individuals.
A few variables from the birth certificates, age of mother or father, race,
Hispanic origin, marital status of mother, gestation period, and plurality were
imputed.
Variables beginning with the letters NTFL... are reporting flags which indicate
whether or not the specified item is included on the birth certificates of the
state of residence OR that the SMSA of residence is composed entirely of state(s)
which report the specified item.
Variables that contain a blank or missing value on a record indicate that the
variable did not appear on that state's birth certificates. Variables that
contain a code of 8, 88, 888, etc. where the documentation says the code stands
for "blank but applicable" indicate that the item to be completed did appear on
the state's standard birth certificate but there was no codable value on the
birth record for this particular child.
Analysts should use caution when using NTOUTCOM (outcome of previous delivery),
interval since last delivery (NTINDLVR), interval since last pregnancy
(NTINTPGR), and interval since last other termination (NTISLTR). These variables
were not computed if the month or year of last other termination was blank even
when it is clear that the mother never had any fetal deaths, miscarriages, or
abortions. For example, the total birth order may be stated as 2, the number of
previous live births may be stated as 1, and the month and year of last live
birth may be given. It seems obvious that the mother had no other terminations,
but if the date of last other termination was blank on the birth certificate
file, the NTOUTCOM variable was not computed (it is blank) and the other
intervals that involve the date of last other termination (NTINDLVR, NTINTPGR,
and NTISLTR) are blank.
DMPFSEQ: Family sequence number
This variable can be used to determine all family members who participated in the
survey. Sample persons who have identical family sequence numbers (i.e., match
on all 5 digits) are members of the same family.
DMPSTAT: Examination/interview status
This variable identifies the interview or examination status of all persons
selected for the NHANES III sample. Interviewed persons completed preselected
questions in specific sections of the Household Adult or Youth Questionnaires.
Mobile examination center (MEC) examined persons were interviewed and
successfully completed at least one examination component in the MEC.
Home-examined persons were interviewed and successfully completed at least one
home examination component. The home examination was an option for frail older
adults, infants 2-11 months of age, and other adults who were unable to come to
the MEC.
DMARETHN: Race-ethnicity
This variable, based on the NHANES III survey design, was derived from many
sources of data and is based on reported race and ethnicity. The "Other"
category includes all Hispanics, regardless of race, who were not
Mexican-American and also includes all non-Hispanics from racial groups other
than white or black.
DMARACER: Race
This variable was obtained from two primary sources: the Screener and the Family
Questionnaire. Prior to the selection of the sample, race (Black, White, Other)
was self-reported or reported by proxy in the Screener Questionnaire. During the
administration of the Family Questionnaire, race was self-reported or reported by
the respondent of the Family Questionnaire from five categories (Aleut, Eskimo,
American Indian; Asian or Pacific Islander; Black; White; Other). Responses from
the two sources were adjudicated, as necessary, to create a three level variable
(Black, White, Other).
DMAETHNR: Ethnicity
This variable was obtained from two primary sources: the Screener and the Family
Questionnaire. As part of both interviews, hand cards were used to determine
Mexican/Mexican-American or Other Latin American/ Spanish ancestry or national
origin. Responses of non-Hispanic ancestry or national origin were categorized
as "Other." Responses from the two interviews were adjudicated, as necessary,
and this three level variable was created.
HSAGEIR: Age at interview (Screener)
Age is calculated using the birth date which is obtained from the Screener
Questionnaire. The variable HSAGEU provides the age unit (months or years) for
HSAGEIR.
HSAITMOR: Age at interview in months (Screener)
Age of the sample child in months is calculated by computing number of months
between the Screener Questionnaire date and the child's date of birth. This
variable is created for analyses where exact age at the interview is needed.
HSAITMOR differs slightly from the age in years (HSAGEIR), the variable most
often used for analyses.
HSFSIZER: Family Size
Family size represents the total number of related persons living in a household
(single dwelling unit). All household members are rostered by family during the
Screener interview. Household members related to the family reference person
(knowledgeable household member 17 years or older who owned or rented the
dwelling unit) by blood or marriage are considered part of the family. Adopted
children, foster- and god-children are also included, if they were living in the
dwelling unit. However, family members who are away at college or living
independently are not included. Other household members who were unrelated to
the reference person are considered members of separate families. See note for
Household Size (HSHSIZER).
HSHSIZER: Household Size
Household size represents the total number of persons living in a single dwelling
unit, both related and unrelated. All permanent household members are rostered
according to their family as part the Screener interview. This is done in order
to obtain a complete list of all persons living or staying in the dwelling unit,
and to distinguish household and family members. See note for Family Size
(HFHSIZER).
DMPMETRO: Urbanization classification based on USDA Rural-Urban continuum codes
These classifications are based on the USDA Rural-Urban codes (Butler and Beale,
1993) that describe metropolitan and non-metropolitan counties by degree of
urbanization and nearness to metropolitan areas. The USDA codes are recoded into
two categories to prevent identification of counties that were sampled in the
survey.
DMPCREGN: Census region
The United States was divided into four broad geographic regions as defined by
the Bureau of Census. Because all states were not included in the selected
sample, regional estimates may not be representative for a given region.
DMPPIR: Poverty income ratio (or poverty index)
The poverty income ratio (PIR) is computed as a ratio of two components. The
numerator is the midpoint of the observed family income category in the Family
Questionnaire variable: HFF19R. The denominator is the poverty threshold based
on the family composition, the age of family reference person, and the calendar
year in which the family was interviewed.
Poverty threshold values (in dollars) are produced annually by the Census Bureau
(Series P-60). These threshold values are based on calendar years and adjusted
for changes caused by inflation between calendar years. Reports for each of the
calendar years in the survey (1988-94) were used in the calculation of PIR. For
the years 1991 and 1994, data from preliminary reports were used. The poverty
income ratio allows income data to be analyzed in a comparable manner across the
six years of the survey and with previous NHANES.
Persons who reported having had no income are assigned a zero value for PIR. A
substantial proportion of persons refused to report their income or income
category during the Family Questionnaire. Due to the income nonresponse the
potential for bias in PIR may be high. Users are cautioned to examine potential
nonresponse bias for PIR and other income variables.
Survey Design Data
SDPPHASE: Phase of NHANES III survey
For operational purposes, 81 primary sampling units are divided into 89 survey
locations (or stands) and randomly allocated to two three-year phases. Phase 1
data were collected from October 1988 through October 1991 and Phase 2 data were
collected from October 1991 through October 1994.
SDPPSU6, SDPPSU1, SDPPSU2 and SDPSTRA6, SDPSTRA1, SDPSTRA2: Pseudo PSU pair
codes and pseudo strata codes
Because NHANES III is based upon a complex sample design, the assumptions of many
statistical tests and routinely available statistical programs are not met. For
this reason, when estimates of the variances of statistics are computed, the
technique of estimation must be based upon complex sampling theory. In order to
provide users with the capability of estimating the complex sample variances, 49
pseudo strata and a pair of Primary Sampling Unit (PSU) codes per stratum were
designed.
A software package, "SUDAAN- Software for the Statistical Analysis of Correlated
Data" (Shah, 1995), was developed by the Research Triangle Institute to analyze
complex sample design data like NHANES. SUDAAN uses strata and PSU codes to
conduct analysis with two PSU per stratum design. Therefore, definitions of
pseudo strata and PSU provided in this data file should be used to compute
complex sample variances in analyses. Other software available for estimation of
complex sample variance may also be used. For further discussion of methods of
variance estimation in NHANES III, see additional information on this subject in
Weighting and Estimation Methodology (U.S. DHHS, 1996) and NHANES III Analytic
and Reporting Guidelines (U.S. DHHS, 1996).
Sampling Weights
WTPFQX6, WTPFQX1, WTPFQX2: Total NHANES III and phase-specific final interview
weights
These sampling weights are used only for items collected during the household
interviews. To compute final interview weights, final basic weights were first
adjusted for nonresponse to household interview, then post-stratified to the
unpublished Current Population Survey 1990 (Phase 1) and 1993 (Phase 2)
population control estimates of the U.S. population adjusted for undercount.
For details, see Weighting and Estimation Methodology (U.S. DHHS, 1996) and
NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996).
WTPFEX6, WTPFEX1, WTPFEX2: Total NHANES III and phase-specific final MEC
examination weights
These MEC sampling weights are used for analysis of measurements or interview
items collected in the MEC. Persons who were not examined in the MEC have a
sampling weight of zero and should be excluded from analyses. To compute final
MEC examination weights, final interview weights were first adjusted for
nonresponse to MEC examinations, then post-stratified to the unpublished Current
Population Survey 1990 (Phase 1) and 1993 (Phase 2) population control estimates
of the U.S. population adjusted for undercount. For details, see Weighting and
Estimation Methodology (U.S. DHHS, 1996) and NHANES III Analytic and Reporting
Guidelines (U.S. DHHS, 1996).
WTPFHX6, WTPFHX1, WTPFHX2: Total NHANES III and phase-specific MEC+home
examination weights
These MEC+home sampling weights are used for analysis of the examination items
where measurements or interview items were collected in the MEC and home.
Persons who were not examined in the MEC or home have a sampling weight of zero
and should be excluded from analyses. To compute final MEC+home examination
weights, final interview weights were first adjusted for non-response to MEC and
home examinations, then post-stratified to unpublished Current Population Survey
1990 (Phase 1) and 1993 (Phase 2) population control estimates of the U.S.
population adjusted for undercount. No separate sampling weights were computed
for home examinees. For details, see Weighting and Estimation Methodology (U.S.
DHHS, 1996) and NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996).
WTPFALG6, WTPFALG1, WTPFALG2: Total NHANES III and phase-specific allergy
examination subsample weights
These subsample weights are for analysis of allergy measurements. Allergy skin
reactivity tests were administered to all MEC-examined persons aged 6-19 years
and a random half-sample of the adults aged 20-59 years. Eligible MEC-examined
persons who did not complete the allergy tests have a sampling weight of zero and
should be excluded from the analyses. Final MEC examination weights were first
adjusted for selection of the half-sample among adults (20-59 years), and
post-stratified to the unpublished Current Population Survey 1990 (Phase 1) and
1993 (Phase 2) population control estimates of the U.S. population adjusted for
undercount in the final step. For details, see Weighting and Estimation
Methodology (U.S. DHHS, 1996) and NHANES III Analytic and Reporting Guidelines
(U.S. DHHS, 1996).
WTPQRP1--WTPQRP52: Fay's BRR Replicate interview sample weights
To allow for alternative methods to estimate variance, 52 replicate weights were
computed using repeated sampling method where WESVAR or other software that use
repeated samples can be used for estimating variance. Fay's method (see Fay,
1990; Judkins, 1990) was used to draw half samples and adjust sampling weights in
each of the random half samples. Sampling weights in one half sample were
multiplied by the factor k=1.7 and in the other half sample by k=0.3 using the
Fay's method. After this adjustment, sampling weights were further adjusted for
non-response and post-stratified using the same procedure as the final full
sample interview weights. These weights should be used only for estimating
variance of items from the household adult and youth interviews. For details,
see Weighting and Estimation Methodology (U.S. DHHS, 1996) and NHANES III
Analytic and Reporting Guidelines (U.S. DHHS, 1996).
WTPXRP1--WTPXRP52: Fay's BRR Replicate weights for MEC-examined sample
To allow for alternative methods to estimate variance, 52 replicate weights were
computed using repeated sampling method where WESVAR or other BRR type software
can be used to estimate variance. Fay's method (see Fay, 1990; Judkins, 1990)
was used to draw half samples and adjust sampling weights in each of the random
half samples. Sampling weights in one half sample were multiplied by the factor
k=1.7 and in the other half sample by k=0.3 using Fay's method. After this
adjustment, weights were further adjusted for nonresponse and were
post-stratified using the same procedure as the full sample final weights. These
weights should be used only for estimating variance of outcome measurements or
interview items from the MEC Examination. For details, see additional
information on this subject in Weighting and Estimation Methodology U.S. DHHS,
1996) and NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996).
Data Based on Birth Certificates
FOR IMPORTANT ADDITIONAL INFORMATION AND DEFINITIONS REGARDING THE
BIRTH CERTIFICATE VARIABLES WHICH ALL BEGIN WITH THE LETTERS "NT", PLEASE BE
SURE TO READ THE SECTION ENTITLED: CLASSIFICATION IN "Vital Statistics
Classification and Coding Instructions for Live Birth Records, 1994," NCHS
Instruction Manual, Part 3a.
The general rules used to classify geographic and personal items for live births
are set forth in "Vital Statistics Classification and Coding Instructions for
Live Birth Records, 1994," NCHS Instruction Manual, Part 3a. The classification
of certain important items is discussed in the following pages.
The rules followed in the classification of geographic areas for live births are
contained in the instruction manual mentioned previously. The geographic code
structure is in another manual, "Vital Records Geographic Classification, 1982,"
NCHS Instruction Manual, Part 8.
NTCERT: Certificate availability
If a matching birth certificate could not be obtained for any reason, this
variable was coded 2. Reasons for failure to obtain a matching certificate
included inability to obtain parental consent, state unable to locate matching
certificate, incorrect last name, missing or incorrect mother's maiden name,
adopted children, incorrect birth date, wrong state or county listed on consent
form, etc.
NTRSTATR: Resident status recode
Code 3, "Nonresident: State of occurrence and residence are different or mother
is foreign," includes three cases where the mother resides outside of the United
States, according to the birth certificate.
NTPLDEL and NTBIRATT: Place or facility of birth and attendant
The 1989 revision of the U.S. Standard Certificate of Live Birth includes
separate categories for freestanding birthing centers, the mother's residence,
and clinic or doctor's office as the place of birth. In previous years, place of
birth was classified simply as either "In hospital" or "Not in hospital." Births
occurring in hospitals, institutions, clinics, centers, or homes were included in
the category "In hospital." In this context the word "homes" does not refer to
the mother's residence but to an institution, such as a home for unmarried women.
Birthing centers were included in either category, depending on each State's
assessment of the facility. Beginning in 1989, births occurring in clinics and
in birthing centers not attached to a hospital are classified as "Not in
hospital."
The "Not in hospital" category includes births for which no information is
reported on place of birth. Babies born on the way to or on arrival at the
hospital are classified as having been born in the hospital. This may account
for some of the hospital births not delivered by physicians or midwives.
NTMETROR: Metropolitan-nonmetropolitan county of residence recode
Metropolitan statistical areas are those established by the U.S. Office of
Management and Budget as of April 1, 1990, and used by the U.S. Bureau of the
Census (U.S. Bureau of the Census, 1991) except in the New England States.
Except in the New England States, an MSA has either a city with a population of
at least 50,000, or a Bureau of the Census urbanized area of at least 50,000 and
a total MSA population of at least 100,000.
In the New England States, the U.S. Office of Management and Budget uses towns
and cities rather than counties as geographic components of MSAs. NCHS cannot,
however, use this classification for these States because its data are not coded
to identify all towns. Instead, the New England County Metropolitan Areas
(NECMAs) are used. These areas are established by the U.S. Office of Management
and Budget (U.S. Office of Management and Budget, 1975) and are made up of county
units.
Independent cities and counties included in MSAs or NECMAs are included in data
for metropolitan counties; all other counties are classified as nonmetropolitan.
Code 2, "Nonmetropolitan county or foreign", includes three cases where the
mother resides outside of the United States, according to the birth certificate.
NTMAGEFL: Reported age of mother used flag
This variable indicates whether the mother's age is derived from the mother's
date of birth or from her age in years.
Beginning in 1989 an item on the birth certificate asks for "Date of Birth." In
previous years, "Age (at time of this birth)" was requested. Not all States have
revised this item, and therefore the age of mother either is derived from the
reported month and year of birth or coded as stated on the certificate. The age
of mother is edited for upper and lower limits. When the age of mother is
computed to be under 10 years or 50 years or over, it is considered not stated
and is assigned as described below.
NTMAGEIM: Age of mother imputation flag
Not stated date of birth of mother -- Beginning in 1964 birth records with date
of birth of mother and/or age of mother not stated have had age imputed according
to the age of mother from the previous birth record of the same race and
total-birth order (total of fetal deaths and live births). (See "Vital Statistics
Computer Edits for Natality Data," NCHS Instruction Manual, Part 12, page 9.)
NTMEDUCR: Education of mother recode
The educational attainment of either parent is defined as "the number of years of
school completed." Only those years completed in "regular" schools are counted,
that is, a formal educational system of public schools or the equivalent in
accredited private or parochial schools. Business or trade schools, such as
beauty and barber schools, are not considered "regular" schools for the purposes
of this item. No attempt has been made to convert years of school completed in
foreign school systems, ungraded school systems, and so forth, to equivalent
grades in the American school system. Such entries are included in the category
"Not stated."
Persons who have completed only a partial year in high school or college are
tabulated as having completed the highest preceding grade. For those
certificates on which a specific degree is stated, years of school completed is
coded to the level at which the degree is most commonly attained; for example,
persons reporting B.A., A.B., or B.S. degrees are considered to have completed 16
years of school.
Education not stated -- The category "Not stated" includes all records in
reporting areas for which there is no information on years of school completed as
well as all records for which the information provided is not compatible with
coding specifications.
NTMMRST: Marital status
Beginning in 1980, a birth in a nonreporting State is classified as occurring to
a married woman if the parents' surnames are the same, or if the child's and
father's surnames are the same and the mother's current surname cannot be
obtained from the informant item of the birth certificate. A birth is classified
as occurring to an unmarried woman if the father's name is missing, if the
parents' surnames are different, or if the father's and child's surnames are
different and the mother's current surname is missing.
When births to unmarried women are reported as second or higher-order births, it
is not known whether the mother was married or unmarried when the previous
deliveries occurred, because her marital status at the time of these earlier
births is not available from the birth record.
NTADEQUA: Adequacy of care recode (Kessner index)
This recode is based on a modified Kessner criterion. Month Prenatal Care Began,
Number of Prenatal Visits, and Gestation are the items used to generate this
recode.
NTISLLBR: Interval since last live birth recode
The interval since the last live birth is the difference in months between the
date of last live birth and the date of present birth. For an interval to be
computed, both the month and year of the last live birth must be valid. This
interval is computed only for events to mothers who have had at least one
previous live birth.
Zero interval - An interval of zero months since the last live birth indicates
the second born of a set of twins, the second or third born of a set of triplets,
and so forth.
NTISLTR: Interval since last other termination recode
This number is the difference in months between the date of the last "other
termination" (non-live birth prior to the NHANES III sample child) and the date
of the NHANES III child's birth. The interval is computed only if month and year
of last other termination are valid. The interval is computed only if the mother
has had a previous pregnancy that terminated in a non-live birth.
NTINDLVR: Interval between deliveries recode
This variable is the number of months between the delivery just prior to that of
the sample child and the date of birth of the sample child. It is calculated by
subtracting the date of the previous delivery (prior to the NHANES III sample
child) from the date of the NHANES III child's birth. An interval of zero
indicates that the sample child is the second or higher order child of a multiple
pregnancy. The interval is computed only if both the month and year of the
previous delivery are valid. The date of previous delivery depends on the
presence of both a valid date of last live birth and a valid date of last other
termination. The interval is calculated only for cases where the mother had a
delivery prior to that of the sample child.
NTOUTCOM: Outcome of last delivery
This variable refers to the delivery immediately prior to the birth of the sample
child. NTOUTCOM was calculated only if both month and year of last live birth
and last other termination were valid. If the sample child is the second or
higher order born of a multiple pregnancy, NTOUTCOM, if present, reflects the
outcome of the delivery just prior to the sample child, i.e., the older twin,
triplet, etc.
NTINTPGR: Interval since last pregnancy recode
This variable represents the interval in months between the end of the last
pregnancy and the beginning of the pregnancy with the sample child. The variable
was computed using the date of last menstrual period (LMP), the date of last live
birth, and the date of last other termination. NTINTPGR was not calculated if
the month or year of LMP, of last live birth and last other termination are not
all valid. Since the date of LMP is prior to the date of last live birth or
other termination in a multiple delivery where the sample child is not the first
born of the multiples, NTINTPGR is 0.
NTLBOR: Live birth order recode
Live-birth order indicates what number the NHANES III sample child represents;
for example, a baby born to a mother who has had two previous live births (even
if one or both are not now living) has a live-birth order of three. Live-birth
order is determined from two items on the birth certificate, "Live births now
living" and "Live births now dead."
NTMONPRE: Month of pregnancy prenatal care began
For those records in which the name of the month is entered for this item instead
of first, second, third, and so forth, the month of pregnancy in which prenatal
care began is determined from the month named and the month last normal menses
began. For these births, if the item "Date last normal menses began" is not
stated, the month of pregnancy in which prenatal care began is tabulated as not
stated.
NTFAGEFL: Reported age of father used flag
A code of 1 indicates that the father's age as reported in years on the
certificate was used rather than the father's date of birth, which was not on the
certificate.
NTFAGER: Age of father recode
Age of father is derived from the reported date of birth or coded as stated on
the birth certificate. If the age is under 10 years, it is considered not stated
and grouped with those cases for which age is not stated on the certificate.
NTFEDUCR: Education of father recode
The educational attainment of either parent is defined as "the number of years of
school completed." Only those years completed in "regular" schools are counted,
that is, a formal educational system of public schools or the equivalent in
accredited private or parochial schools. Business or trade schools, such as
beauty and barber schools, are not considered "regular" schools for the purposes
of this item. No attempt has been made to convert years of school completed in
foreign school systems, ungraded school systems, and so forth, to equivalent
grades in the American school system. Such entries are included in the category
"Not stated."
Persons who have completed only a partial year in high school or college are
tabulated as having completed the highest preceding grade. For those
certificates on which a specific degree is stated, years of school completed is
coded to the level at which the degree is most commonly attained; for example,
persons reporting B.A., A.B., or B.S. degrees are considered to have completed
16 years of school.
Education not stated--The category "Not stated" includes all records in reporting
areas for which there is no information on years of school completed as well as
all records for which the information provided is not compatible with coding
specifications.
NTGESTFL: Clinical estimate of gestation used flag; and
NTGESTR: Period of gestation recode
The period of gestation is defined as beginning with the first day of the last
normal menstrual period (LMP) and ending with the day of the birth. The LMP is
used as the initial date because it can be more accurately determined than the
date of conception, which usually occurs 2 weeks after the LMP.
Births occurring before 37 completed weeks of gestation are considered to be
"preterm" or "premature" for purposes of classification. At 37-41 weeks
gestation, births are considered to be "term," and at 42 completed weeks and
over, "postterm." These distinctions are according to the ICD-9 definitions.
The 1989 revision of the U.S. Standard Certificate of Live Birth includes a new
item, "clinical estimate of gestation," that is being compared with length of
gestation computed from the LMP date when the latter appears to be inconsistent
with birth weight. This is done for normal-weight births of apparently short
gestations and very low-birth weight births reported to be full term. The
clinical estimate also was used if the date of the LMP was not reported. In
cases where the reported birth weight was inconsistent with both the LMP-computed
gestation and the clinical estimate of gestation, the LMP-computed gestation was
used and birth weight was reclassified as "not stated." These changes result in
only a very small discontinuity in the data. For further information on the use
of the clinical estimate of gestation see "Computer Edits for Natality Data,
Effective 1989," NCHS Instruction Manual, Part 12, pages 34-36.
Beginning in 1981, weeks of gestation have been imputed for records with missing
day of LMP when there is a valid month and year. Each such record is assigned
the gestational period in weeks of the preceding record that has a complete LMP
date with the same computed months of gestation and the same 500-gram birth
weight interval. The effect of the imputation procedure is to increase slightly the
proportion of preterm births and to lower the proportion of births at 39, 40, 41,
and 42 weeks of gestation. A more complete discussion of this procedure and its
implications is presented in a previous report (Taffel S, Johnson D, Heuser R,
1982).
Because of postconception bleeding or menstrual irregularities, the presumed date
of LMP may be in error. In these instances the computed gestational period may
be longer or shorter than the true gestational period, but the extent of such
errors is unknown.
NTSEX and NTCRACE: Sex of child and Race of child
These items may differ from the values recorded in NHANES III for this child.
The NTSEX and NTCRACE variables came from the birth certificate.
NTPLURR: Plurality recode
Plurality refers to a multiple pregnancy, i.e., twins, triplets, etc. If the
child on the certificate was part of a multiple pregnancy, this variable will
reflect that status regardless of the birth order within the multiples. Even if
the other twin, triplet, etc. was a fetal death, the plurality variable will
still reflect the multiple pregnancy.
NTOMAPSR and NTFMAPSR: One minute and Five minute Apgar score recodes
One- and 5-minute Apgar scores were added to the U.S. Standard Certificate of
Live Birth in 1978 to evaluate the condition of the newborn infant at 1 and 5
minutes after birth. The Apgar score is a useful measure of the need for
resuscitation and a predictor of the infant's chances of surviving the first year
of life. It is a summary measure of the infant's condition based on heart rate,
respiratory effort, muscle tone, reflex irritability, and color. Each of these
factors is given a score of 0, 1, or 2; the sum of these 5 values is the Apgar
score, which ranges from 0 to 10. A score of 10 is optimal, and a low score
raises some doubts about the survival and subsequent health of the infant.
NTVAGINA, NTVBAC, NTPRIMAC, NTREPEAC, NTDELIVR, NTFORCEP, NTVACUUM:
Methods of delivery - Vaginal, Vaginal birth after previous C-section, Primary
C-section, Repeat C-section, Vaginal or C-section recode, Forceps, and Vacuum.
The birth certificate contains a check box item on method of delivery. The
choices include vaginal delivery, with the additional options of forceps, vacuum,
and vaginal birth after previous cesarean section (VBAC), as well as a choice of
primary or repeat cesarean. When only forceps, vacuum, or VBAC is checked, a
vaginal birth is assumed.
NTAORHR, NTCARDIA, NTLUNG, NTDIABET, NTHERPES, NTHYDRA, NTCHYPER,
NTPHYPER, NTECLAMP, NTINCERV, NTPR4000, NTPRTERM, NTRENAL, NTRH, NTUTERIN,
NTOTHRMR:
Medical risk factors for this pregnancy - Anemia or hemoglobinopathy recode (also
see separate note below for NTAORHR), Cardiac disease, Acute or chronic lung
disease, Diabetes, Genital herpes, Hydramnios/Olighydramnios, Chronic
hypertension, Pregnancy-associated hypertension, Eclampsia, Incompetent cervix,
Previous infant 4000+ grams, Previous infant preterm or small for gestational
age, Renal disease, RH sensitization, Uterine bleeding, or Other medical risk
factors
The birth certificate format allows for the designation of more than one risk
factor and includes a choice of "None." Accordingly, if the item is not
completed, it is classified as "Not stated."
The following definitions are adapted and abbreviated from a set of definitions
compiled by a committee of Federal and State health statistics officials for the
Association for Vital Records and Health Statistics (Brockert JE, Stockbauer JW,
Senner JW, et al, 1990).
Anemia--Hemoglobin level of less than 10.0 g/dL during pregnancy or a hematocrit
of less than 30 percent during pregnancy.
Cardiac disease--Disease of the heart.
Acute or chronic lung disease--Disease of the lungs during pregnancy.
Diabetes--Metabolic disorder characterized by excessive discharge of urine and
persistent thirst; includes juvenile onset, adult onset, and gestational diabetes
during pregnancy.
Genital herpes--Infection of the skin of the genital area by herpes simplex
virus.
Hydramnios/Oligohydramnios--Any noticeable excess (hydramnios) or lack
(oligohydramnios) of amniotic fluid.
Hemoglobinopathy--A blood disorder caused by alteration in the genetically
determined molecular structure of hemoglobin (for example, sickle cell anemia).
Hypertension, chronic--Blood pressure persistently greater than 140/90, diagnosed
prior to onset of pregnancy or before the 20th week of gestation.
Hypertension, pregnancy-associated--An increase in blood pressure of at least 30
mm Hg systolic or 15 mm Hg diastolic on two measurements taken 6 hours apart
after the 20th week of gestation.
Eclampsia--The occurrence of convulsions and/or coma unrelated to other cerebral
conditions in women with signs and symptoms of pre-eclampsia.
Incompetent cervix--Characterized by painless dilation of the cervix in the
second trimester or early in the third trimester of pregnancy, with prolapse of
membranes through the cervix and ballooning of the membranes into the vagina,
followed by rupture of membranes and subsequent expulsion of the fetus.
Previous infant 4,000+ grams--The birth weight of a previous live-born child was
over 4,000 grams (8 lbs 13 oz).
Previous preterm or small-for-gestational-age infant--Previous birth of an infant
prior to term (before 37 completed weeks of gestation) or of an infant weighing
less than the 10th percentile for gestational age using a standard weight-for-age
chart.
Renal disease--Kidney disease.
Rh sensitization--the process or state of becoming sensitized to the Rh factor as
when an Rh-negative woman is pregnant with an Rh-positive fetus.
Uterine bleeding--Any clinically significant bleeding during the pregnancy,
taking into consideration the stage of pregnancy; any second or third trimester
bleeding of the uterus prior to the onset of labor.
NTAORHR: Anemia or hemoglobinopathy recode
The anemia and hemoglobinopathy variables are combined due to small cell sizes in
order to prevent potential identification of individuals.
NTTOBACR, NTCIGARR, NTALCOHR, NTDRINKR: Tobacco and alcohol use during
pregnancy recodes
The check box format on the birth certificate allows for classification of a
mother as a smoker or drinker during pregnancy and for reporting the average
number of cigarettes smoked per day or drinks consumed per week. When smoking
and/or drinking status is not reported or is inconsistent with the quantity of
cigarettes or drinks reported, the status is changed to be consistent with the
amount reported. For example, if the drinking status is reported as "no" but one
or more average drinks a week are reported, the mother is classified as a
drinker. If the number of cigarettes smoked per day is reported as one or more,
the mother is considered a smoker. When one (or a fraction of one) drink a week
is recorded, the mother is classified as a drinker. For records on which the
number of drinks or number of cigarettes is reported as a span, for example,
10-15, the lower number is used. The number of drinkers and number of drinks
reported on birth certificates are believed to underestimate actual alcohol use.
NTWTGNR: Weight gain (during pregnancy) recode
Weight gain is reported in pounds. A loss of weight is reported as zero gain.
NTAMNIO, NTMONITO, NTINDUCT, NTSTIMUL, NTTOCOL, NTULTRAS, NTOTHROB:
Obstetric procedures - Amniocentesis, Electronic fetal monitoring, Induction of
labor, Stimulation of Labor, Tocolysis, Ultrasound, Other obstetric procedures.
This birth certificate item includes six specific obstetric procedures. Birth
records with "Obstetric procedures" left blank are considered "not stated."
The following definitions are adapted and abbreviated from a set of definitions
compiled by a committee of Federal and State health statistics officials for the
Association for Vital Records and Health Statistics (Brockert JE, Stockbauer JW,
Senner JW, et al, 1990).
Amniocentesis--Surgical transabdominal perforation of the uterus to obtain
amniotic fluid to be used in the detection of genetic disorders, fetal
abnormalities, and fetal lung maturity.
Electronic fetal monitoring--Monitoring with external devices applied to the
maternal abdomen or with internal devices with an electrode attached to the fetal
scalp and a catheter through the cervix into the uterus, to detect and record
fetal heart tones and uterine contractions.
Induction of labor--The initiation of uterine contractions before the spontaneous
onset of labor by medical and/or surgical means for the purpose of delivery.
Stimulation of labor--Augmentation of previously established labor by use of
oxytocin.
Tocolysis--Use of medications to inhibit preterm uterine contractions to extend
the length of pregnancy and therefore avoid a preterm birth.
Ultrasound--Visualization of the fetus and placenta by means of sound waves.
NTFEBRIL, NTMECONI, NTRUPTUR, NTABRUPT, NTREPLAC, NTEXCBLD,
NTSEIZUR, NTPRECIP, NTPRLONG, NTDYSFUN, NTBREECH, NTCEPHAL, NTCORD,
NTANESTH, NTDISTRE,NTOTHRLB:
Complications of labor and/or delivery - Febrile, Meconium- moderate/heavy,
Premature rupture of membrane, Abruptio placenta, Placenta previa, Other
excessive bleeding, Seizures during labor, Precipitous labor, Prolonged labor,
Dysfunctional labor, Breech/malpresentation, Cephalopelvic disproportion, Cord
prolapse, Anesthetic complications, Fetal distress, Other complications of labor
and/or delivery.
The birth certificate check box format allows for the selection of 15 specific
complications and for the designation of more than 1 complication where
appropriate. A choice of "None" is also included. Accordingly, if the item is
not completed, it is classified as "not stated." Not all of the complications
were reported by all reporting States.
The following definitions are adapted and abbreviated from a set of definitions
compiled by a committee of Federal and State health statistics officials for the
Association for Vital Records and Health Statistics (Brockert JE, Stockbauer JW,
Senner JW, et al, 1990).
Febrile--A fever greater than 100 degrees F. or 38 C. occurring during labor
and/or delivery.
Meconium, moderate/heavy--Meconium consists of undigested debris from swallowed
amniotic fluid, various products of secretion, excretion and shedding by the
gastrointestinal tract; moderate to heavy amounts of meconium in the amniotic
fluid noted during labor and/or delivery.
Premature rupture of membranes (more than 12 hours)--Rupture of the membranes at
any time during pregnancy and more than 12 hours before the onset of labor.
Abruptio placenta--Premature separation of a normally implanted placenta from the
uterus.
Placenta previa--Implantation of the placenta over or near the internal opening
of the cervix.
Other excessive bleeding--The loss of a significant amount of blood from
conditions other than abruptio placenta or placenta previa.
Seizures during labor--Maternal seizures occurring during labor from any cause.
Precipitous labor (less than 3 hours)--Extremely rapid labor and delivery lasting
less than 3 hours.
Prolonged labor (more than 20 hours)--Abnormally slow progress of labor lasting
more than 20 hours.
Dysfunctional labor--Failure to progress in a normal pattern of labor.
Breech/Malpresentation--At birth, the presentation of the fetal buttocks rather
than the head, or other malpresentation.
Cephalopelvic disproportion--The relationship of the size, presentation and
position of the fetal head to the maternal pelvis prevents dilation of the cervix
and/or descent of the fetal head.
Cord prolapse--Premature expulsion of the umbilical cord in labor before the
fetus is delivered.
Anesthetic complications--Any complication during labor and/or delivery brought
on by an anesthetic agent or agents.
Fetal distress--Signs indicating fetal hypoxia (deficiency in amount of oxygen
reaching fetal tissues).
NTNANEMI, NTINJURY, NTALCOSY, NTHYALIN, NTMECONS, NTVENL30,
NTVEN30M, NTOTHABR:
Abnormal conditions of the newborn - Anemia, Birth injury, Fetal alcohol
syndrome, Hyaline membrane disease, Meconium aspiration syndrome, Assisted
ventilation less than 30 minutes, Assisted ventilation 30 minutes or more, Other
abnormal conditions of the newborn recode.
This certificate item provides information on eight specific abnormal conditions.
More than one abnormal condition may be reported for a given birth or "None" may
be selected. If the item is not completed it is tabulated as "not stated."
The following definitions are adapted and abbreviated from a set of definitions
compiled by a committee of Federal and State health statistics officials for the
Association for Vital Records and Health Statistics (Brockert JE, Stockbauer JW,
Senner JW, et al, 1990).
Anemia--Hemoglobin level of less than 13.0 g/dL or a hematocrit of less than 39
percent.
Birth injury--Impairment of the infant's body function or structure due to
adverse influences that occurred at birth.
Fetal alcohol syndrome--A syndrome of altered prenatal growth and development
occurring in infants born of women who consumed excessive amounts of alcohol
during pregnancy.
Hyaline membrane disease/RDS--A disorder primarily of prematurity, manifested
clinically by respiratory distress and pathologically by pulmonary hyaline
membranes and incomplete expansion of the lungs at birth.
Meconium aspiration syndrome--Aspiration of meconium by the fetus or newborn,
affecting the lower respiratory system.
Assisted ventilation (less than 30 minutes)--A mechanical method of assisting
respiration for newborns with respiratory failure.
Assisted ventilation (30 minutes or more)--Newborn placed on assisted ventilation
for 30 minutes or longer.
Seizures--A seizure of any etiology.
NTOTHABR: Other abnormal conditions of the newborn recode
This category includes seizures. The two categories were combined because of
small cell sizes in order to prevent potential identification of individuals.
NTCIRCUL, NTCLUBFT, NTMUSCUL, NTCONMJR, NTCONMNR: Congenital anomalies
of child - Other circulatory/respiratory anomalies, Club foot, Other
musculoskeletal/integumental anomalies, Major congenital anomalies recode, Minor
congenital anomalies recode.
The data provided in this certificate item relate to 21 specific anomalies or
anomaly groups. It is well documented that congenital anomalies, except for the
most visible and most severe, are incompletely reported on birth certificates.
The completeness of reporting specific anomalies depends on how easily they are
recognized in the short time between birth and birth registration. The format
allows for the identification of more than one anomaly including a choice of
"None" should no anomalies be evident. The category "not stated" includes birth
records for which the item is not completed.
The following definitions are adapted and abbreviated from a set of definitions
compiled by a committee of Federal and State health statistics officials for the
Association for Vital Records and Health Statistics (Brockert JE, Stockbauer JW,
Senner JW, et al, 1990).
Anencephalus--Absence of the cerebral hemispheres.
Spina Bifida/meningocele--Developmental anomaly characterized by defective
closure of the bony encasement of the spinal cord, through which the cord and
meninges may or may not protrude.
Hydrocephalus--Excessive accumulation of cerebrospinal fluid within the
ventricles of the brain with consequent enlargement of the cranium.
Microcephalus--A significantly small head.
Other central nervous system anomalies--Other specified anomalies of the brain,
spinal cord, and nervous system.
Heart malformations--Congenital anomalies of the heart.
Other circulatory/respiratory anomalies--Other specified anomalies of the
circulatory and respiratory systems.
Rectal atresia/stenosis--Congenital absence, closure, or narrowing of the rectum.
Tracheo-esophageal fistula/Esophageal atresia--An abnormal passage between the
trachea and the esophagus; esophageal atresia is the congenital absence or
closure of the esophagus.
Omphalocele/gastroschisis--An omphalocele is a protrusion of variable amounts of
abdominal viscera from a midline defect at the base of the umbilicus. In
gastroschisis, the abdominal viscera protrude through an abdominal wall defect,
usually on the right side of the umbilical cord insertion.
Other gastrointestinal anomalies--Other specified congenital anomalies of the
gastrointestinal system.
Malformed genitalia--Congenital anomalies of the reproductive organs.
Renal agenesis--One or both kidneys are completely absent.
Other urogenital anomalies--Other specified congenital anomalies of the organs
concerned in the production and excretion of urine, together with organs of
reproduction.
Cleft lip/palate--Cleft lip is a fissure of elongated opening of the lip; cleft
palate is a fissure in the roof of the mouth. These are failures of embryonic
development.
Polydactyly/syndactyly/adactyly--Polydactyly is the presence of more than five
digits on either hands and/or feet; syndactyly is having fused or webbed fingers
and/or toes; adactyly is the absence of fingers and/or toes.
Club foot--Deformities of the foot, which is twisted out of shape or position.
Diaphragmatic hernia--Herniation of the abdominal contents through the diaphragm
into the thoracic cavity usually resulting in respiratory distress.
Other musculoskeletal/integumental anomalies--Other specified congenital
anomalies of the muscles, skeleton, or skin.
Down's syndrome--The most common chromosomal defect with most cases resulting
from an extra chromosome (trisomy 21).
Other chromosomal anomalies--All other chromosomal aberrations.
NTCONMJR: Major congenital anomalies of newborn recode
This variable combines several categories of anomalies because of small cell
sizes and the need to prevent possible identification of individuals.
Anomalies that may have been combined in this category include: Anencephalus,
Spina bifida/meningocele, Hydrocephalus, Microcephalus, Other central nervous
system anomalies, Heart malformations, Tracheo-esophageal fistula/Esophageal
atresia, Omphalocele/gastroschisis, Other gastrointestinal anomalies, Renal
agenesis, Down's syndrome, and Other chromosomal anomalies.
NTCONMNR: Minor congenital anomalies of newborn recode
This variable combines several categories of anomalies because of small cell
sizes and the need to prevent possible identification of individuals.
Anomalies that may have been combined in this category include:
Rectal atresia/stenosis, Malformed genitalia, Other urogenital anomalies, Cleft
lip/palate, Polydactyly/syndactyly/adactyly, Club foot, Diaphragmatic hernia,
Other musculoskeletal/integumental anomalies, and Other congenital anomalies.
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