Reassessing the WIC effect: Evidence from the pregnancy nutrition surveillance system

Recent analyses differ on how effective the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is at improving infant health. We use data from nine states that participate in the Pregnancy Nutrition Surveillance System to address limitations in previous work. With information on the mother's timing of WIC enrollment, we test whether greater exposure to WIC is associated with less smoking, improved weight gain during pregnancy, better birth outcomes, and greater likelihood of breastfeeding. Our results suggest that much of the often reported association between WIC and lower rates of preterm birth is likely spunous, the result of gestational age bias. We find modest effects of WIC on fetal growth, inconsistent associations between WIC and smoking, limited associations with gestational weight gain, and some relationship with breastfeeding. A WIC effect exists, but on fewer margins and with less impact than has been claimed by policy analysts and advocates.