In the population that ... received WIC assistance, average birth weight increased by approximately 29 grams, or 10 percent.
The Supplemental Program for Women, Infants and Children (WIC), established in 1972, directly aids low-income pregnant and lactating women and young children by providing nutritional counseling and food vouchers for items including eggs, cheese, milk, tuna, carrots and iron-fortified infant formula. Widely used and broadly supported, WIC has a current annual budget of $6.2 billion. Since the first WIC office opened in Kentucky in 1974, the number of WIC participants has grown from 88,000 to 8.7 million in 2009. A number of previous studies have found that pregnant women who participate in WIC give birth to healthier babies than those who do not.
In Is a WIC Start a Better Start? Evaluating WIC's Impact on Infant Health Using Program Introduction (NBER Working Paper No. 15589), researchers Hilary Hoynes, Marianne Page, and Ann Huff Stevens provide new evidence on the link between infant birth weight and maternal participation in the WIC program. Using the gradual introduction of WIC programs across 2,059 counties between 1972 and 1982 to frame their research, they compare average birthweights within counties before and after WIC adoption. Because some counties adopted WIC earlier than others, the authors are able to disentangle the effects of implementing WIC from the underlying time trend in infant health.
The authors find that in counties and years where the WIC program was implemented, infant health improved. They observe that birth weight outcomes are important, both in their own right and as predictors of later health and socioeconomic success. Analyzing mean birth weight (in grams) and the fraction of newborns classified as "low birth weight" (less than 2,500 grams), they find that WIC availability increased average birth weight by a statistically significant 2.7 grams. When the results are scaled to reflect that only a minority of eligible mothers actually choose to receive WIC, these results suggest that average birth weight among WIC participants increased by approximately 29 grams, or 10 percent.
Educational data on birth certificates helped the authors identify groups for whom WIC participation is higher, and therefore the effects of WIC introduction should be greater. They find that among women with less than a high school education, the availability of WIC food aid increases their infants' average birth weight by 7 grams. They also find that as the mother's educational level increases, the effect of participating in WIC declines, as expected. In addition, they find that the impact of WIC introduction is concentrated in counties with the highest poverty rates. Finally, "WIC access appears to have no impact on the percent of births to mothers with less than a high school education or on the fraction of births to minority mothers," the authors write, making it unlikely that their results are driven by changes in the composition of children born after the program started.
-- Sarah H. Wright