Effects of Participation in the WIC Program on Birthweight: Evidence From the National Longitudinal Survey of Youth

OBJECTIVES: This study sought to estimate the impact on birthweight of maternal participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). METHODS: WIC estimates were based on sibling models incorporating data on children born between 1990 and 1996 to women taking part in the National Longitudinal Survey of Youth. RESULTS: Fixed-effects estimates indicated that prenatal WIC participation was associated with a 0.075 unit difference (95% confidence interval [CI] = -0.007, 0.157) in siblings' logged birthweight. At the 88-oz (2464-g) low-birthweight cutoff, this difference translated into an estimated impact of 6.6 oz (184.8 g). CONCLUSION: Earlier WIC impact estimates may have been biased by unmeasured characteristics affecting both program participation and birth outcomes. Our approach controlled for such biases and revealed a significant positive association between WIC participation and birthweight.