Special Supplemental Nutrition Program for Women, Infants, and Children Enrollment and Adverse Pregnancy Outcomes Among Nulliparous Individuals

To evaluate the relationship between changes in Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) enrollment during pregnancy from 2016 to 2019 and rates of adverse pregnancy outcomes in U.S. counties in 2019. We conducted a serial, cross-sectional ecologic study at the county level using National Center for Health Statistics natality data from 2016 to 2019 of nulliparous individuals eligible for WIC. The exposure was the change in county-level WIC enrollment from 2016 to 2019 (increase [more than 0%] vs no change or decrease [0% or less]). Outcomes were adverse pregnancy outcomes assessed in 2019 and included maternal outcomes (ie, gestational diabetes mellitus [GDM], hypertensive disorders of pregnancy, cesarean delivery, intensive care unit [ICU] admission, and transfusion) and neonatal outcomes (ie, large for gestational age [LGA], small for gestational age [SGA], preterm birth, and neonatal intensive care unit [NICU] admission). Among 1,945,914 deliveries from 3,120 U.S. counties, the age-standardized rate of WIC enrollment decreased from 73.1 (95% CI, 73.0-73.2) per 100 live births in 2016 to 66.1 (95% CI, 66.0-66.2) per 100 live births in 2019, for a mean annual percent change decrease of 3.2% (95% CI, -3.7% to -2.9%) per year. Compared with individuals in counties in which WIC enrollment decreased or did not change, individuals living in counties in which WIC enrollment increased had lower rates of maternal adverse pregnancy outcomes, including GDM (adjusted odds ratio [aOR] 0.71, 95% CI, 0.57-0.89), ICU admission (aOR 0.47, 95% CI, 0.34-0.65), and transfusion (aOR 0.68, 95% CI, 0.53-0.88), and neonatal adverse pregnancy outcomes, including preterm birth (aOR 0.71, 95% CI, 0.56-0.90) and NICU admission (aOR 0.77, 95% CI, 0.60-0.97), but not cesarean delivery, hypertensive disorders of pregnancy, or LGA or SGA birth. Increasing WIC enrollment during pregnancy at the county level was associated with a lower risk of adverse pregnancy outcomes. In an era when WIC enrollment has decreased and food and nutrition insecurity has increased, efforts are needed to increase WIC enrollment among eligible individuals in pregnancy.