Distribution of Select Characteristics Among Participants in the IFPS II and Among Participants in the NSFG (Cycle 6), 2002

CharacteristicPercentage of IFPS II Sample (Mothers of Infants Born in 2005) (N = 3033)aPercentage of NSFG Sample (Mothers of Infants Born in 1998–2000) (N = 1415)b
    18–24 yc23.332.6
    25–34 y61.454.9
    35–43 y15.312.4
Marital status
    Married or cohabitingd79.179.5
    High school or lessc21.047.5
    Some college40.227.8
    College graduate38.824.7
    <185% of FPLc41.945.2
    185–349% of FPL35.827.4
    >350% of FPL22.327.4
Employment status (prenatal)
    Not employed33.738.8
Prenatal smoking
Prenatal care
    <13 wkc88.691.9
    13–21 wk6.95.8
    ≥22 wk/never4.52.3
Total maternity leave taken (paid and unpaid)
    ≤6 wkc21.038.1
    >6 wk79.061.9
  • FPL indicates federal poverty level.

  • a Sample sizes vary slightly because of missing data on some variables.

  • b The NSFG sample was limited to most recent singleton live births to women 18 to 44 years old at delivery. Weighted percentages are reported.

  • c t tests were conducted to evaluate the differences between NSFG and IFPS characteristics, which required that all variables be dichotomized. Multilevel variables were categorized by keeping 1 category and collapsing all others. The b for multilevel variables indicates the category that was kept and that it was significantly different across the 2 samples at P < .05. For dichotomous variables, the b indicates that the variable was significantly different across samples.

  • d Category was kept and was not significantly different across the 2 samples.