IFSS_AGEFSTLB: Age at first live birth
|Summary for Variable Group: Pregnancy and birth history|
|This variable group provides information about the respondent's total number of births, live births, miscarriages or stillbirths, and pregnancies. It also contains information on the century month of her first and most recent live births, her age at first birth, age at menarche, menstrual status, current pregnancy status, and whether she has ever given a baby up for adoption. More complete information on pregnancies and births is located in the pregnancy interval file.
|Age at first live birth|
|1976 NSFG: Interval File|
|BPREC4||Computed||1976 NSFG: Interval File|
|BPREC2||Computed||1976 NSFG: Interval File|
|This variable provides the age (in completed years) of the respondent at her first live birth, including babies who died shortly after birth.
General Comparability Notes
Summary: IFSS_AGEFSTLB is highly comparable across all surveys.
In all years this variable is computed using the century month for the end date of the respondent’s first pregnancy, recorded in IFSS_CMFSTLB, and the respondent's century month of birth, recorded in IFSS_CMBIRTH, according to the formula:
IFSS_AGEFSTLB = trunc[(IFSS_CMFSTLB – IFSS_CMBIRTH)/12].
That is, the respondent's age in years is calculated by calculating the number of months between her birth and her first live birth, dividing by 12, and then rounding to produce the number of completed years.
In all years, pregnancy outcome and end date were asked for every live birth, as was the respondent's date of birth, so the universes are identical across surveys.
Imputation Flag Exists
|Imputation Flag Values|
|1||Imputed in original study|
|3||Month imputed (Original file edit)|
|4||Age known, month imputed|
|5||Originally imputed as June, recoded to random month|
|7||Multiple regression imputed: Not ascertained|
|8||Multiple regression imputed: Refused|
|9||Multiple regression imputed: Don't know|
|10||Midpoint of a given range|
|11||Answer comes from a follow-up question|
|12||Midpoint of a range given as a follow-up|
|13||Answer is rounded up|
|14||Answer is rounded down|
|15||Reported months and weeks, weeks<=4|
|17||Reported months=weeks & weeks>4|
|18||Reported months!=trunc(weeks/4.35), months!=weeks, weeks>4|
|19||Months coded NA/RF/DK|
|20||Weeks coded NA/RF/DK|
|21||Impossible to determine which method used last|