Abstract
OBJECTIVES: We tested the hypothesis that early enrollment in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is associated with a reduced risk of rapid infant weight gain (RIWG). METHODS: We used a longitudinal cohort of mother-infant pairs (n = 157,590) enrolled in WIC in New York State from 2008 to 2009 and estimated the odds of RIWG, defined as a 12-month change in weight-for-age z score of more than .67, comparing infants of mothers enrolled during the first, second, or third trimester of pregnancy with those who delayed enrollment until the postpartum period. RESULTS: After adjusting for potential confounders, the odds of RIWG (odds ratio [OR] = 0.76; 95% confidence interval [CI] = 0.74, 0.79) were significantly lower for infants of women enrolling during the first trimester versus postpartum. Birth weight-for-gestational-age z score (OR = 0.33; 95% CI = 0.32, 0.33) attenuated the estimate of prenatal versus postpartum enrollment (OR = 0.92; 95% CI = 0.88, 0.95; first-trimester enrollees). CONCLUSIONS: The results demonstrate that prenatal WIC participation is associated with reduced risk of RIWG between birth and age 1 year. Improved birth weight for gestational age may be the mechanism through which early prenatal WIC enrollment protects against RIWG.