Distribution of Select Characteristics Among Respondents and Nonrespondents in the Y6FU, Based on Information From the IFPSII

CharacteristicParticipants in the Y6FU (N = 1542), %Nonparticipants in the Y6FU (N = 1416), %χ2 Probability
Maternal characteristics
 Age (y)<.001
 Marital status<.001
  Married or cohabiting83.773.9
  High school or less16.625.8
  Some college37.243.4
  College graduate46.230.8
 Income (% of poverty threshold)<.001
 Employment status (prenatal).30
  Not employed33.034.8
 Race and ethnicity<.01
 Prenatal smoking<.001
 Prenatal care, initial visit (wk)<.01
 Returned to work when infant was ≤6 wk old.29
 Prepregnancy BMI.48
  Underweight (<18.5)4.35.2
  Normal wt (18.5–24.9)44.745.7
  Overweight (25.0–29.9)26.326.0
  Obese (≥30.0)24.723.1
 Number of postnatal questionnaires returned<.001
Infant characteristics
 Breastfeeding initiation.18
 Breastfeeding durationa (wk)<.001
  Breastfeeding at last questionnaire30.129.7
 WIC participation<.001
 Food allergy.17
 Birth wt (lb).06
 Gestational age (wk).37
  • WIC, Special Supplemental Nutrition Program for Women, Infants, and Children.

  • a Breastfeeding duration was divided into categories by tertile among those with a value (ie, those that were not censored), and the censored cases formed a fourth category.