Date of Defense:
May 19, 2016
Newborns born either prematurely (<37 weeks gestation) or small-for-gestational age (SGA, <10% of birth weight for a given gestational age) are at increased risk of infant mortality and lifelong health consequences. The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), a program of the United States Department of Agriculture (USDA), provides nutrition-related services that safeguard the health of low-income pregnant women and may improve birth outcomes in its prenatal participants. The objective of this study was to assess whether trimester of WIC enrollment during pregnancy was associated with differences in SGA and preterm infants born to Minnesota WIC prenatal participants. Using records from the WIC Data System at the Minnesota Department of Health, our study sample included Minnesota WIC prenatal participants who had singleton births in 2013-2014 (n=45,867). We conducted unconditional logistic regression to measure the associations of WIC enrollment timing (modeled as trimester of enrollment) with the binary outcomes of SGA and preterm delivery, controlling for other covariates. Trimester of WIC enrollment was slightly associated with odds of delivering an SGA infant in the unadjusted model, but differences did not persist in the multivariable model (2ndtrimester: adjusted OR=1.03, 95%CI=0.96,1.11; 3rd trimester: adjusted OR 1.02, 95% CI=0.93,1.12 compared to 1st trimester). Both crude and adjusted models showed that later enrollment in the WIC program during pregnancy was associated with lower odds of preterm birth (Adjusted OR=0.91, 0.46 for 2nd and 3rd trimester enrollees, respectively, compared to first trimester enrollees). Benefits of the WIC program may not directly impact birth outcomes but instead come in the form of improvements in diet-related outcomes, infant feeding practices, and other health behaviors. Additionally, future research could assess whether WIC influences birth outcomes in high-risk subgroups, such as those who are underweight or very obese prior to pregnancy or those who smoke prior to pregnancy.