A Quasi-Experimental Assessment of the Effect of the 2009 WIC Food Package Revisions on Breastfeeding Outcomes.

Breastfeeding rates among infants participating in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) are consistently lower than those of WIC nonparticipants. The 2009 WIC food package revisions were intended to incentivize breastfeeding among the WIC population. To examine the effectiveness of this policy change, we estimated an intent-to-treat regression-adjusted difference-in-difference model with propensity score weighting, an approach that allowed us to control for both secular trends in breastfeeding and selection bias. We used novel data from the Feeding Infants and Toddlers Survey from 2008 and 2016. We defined our treatment group as infants eligible for WIC based on household income and our control group as infants in households with incomes just above the WIC eligibility threshold. The breastfeeding outcomes we analyzed were whether the infants were ever breastfed, breastfed through 6 months, and breastfed exclusively through 6 months. We observed significant increases in infants that were ever breastfed in both the treatment group (10 percentage points; p < 0.01) and the control group (15 percentage points; p < 0.05); however, we did not find evidence that the difference between the two groups was statistically significant, suggesting that the 2009 revisions may not have had an effect on any of these breastfeeding outcomes.