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 spurious, 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 breast feeding. A WIC effect exists, but on fewer margins and with less impact than has been claimed by policy analysts and advocates.

Maternal Smoking and the Timing of WIC Enrollment

We investigate the association between the timing of enrollment in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and smoking among prenatal WIC participants. We use WIC data from eight states participating in the Pregnancy Nutrition Surveillance System (PNSS). Women who enroll in WIC in the first trimester of pregnancy are 2.7 percentage points more likely to be smoking at intake than women who enroll in the third trimester. Among participants who smoked before pregnancy and at prenatal WIC enrollment, those who enrolled in the first trimester are 4.5 percentage points more likely to quit smoking 3 months before delivery and 3.4 percentage points more likely to quit by postpartum registration, compared with women who do not enroll in WIC until the third trimester. Overall, early WIC enrollment is associated with higher quit rates, although changes are modest when compared to the results from smoking cessation interventions for pregnant women.