Objectives: The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) aims to safeguard the health of low-income, nutritionally at-risk pregnant and postpartum women and children less than 5 years old. This systematic review evaluates whether participation in WIC is associated with nutrition and health outcomes for women, infants, and children, and whether the associations vary by duration of participation or across subgroups. Because of major revisions to the WIC food package in 2009, we prioritized studies published since 2009 and included studies comparing outcomes before and after the 2009 food package change.
Data sources: Using electronic publication databases, we conducted a literature search from January 2009 to September 2021 and a targeted search for selected outcomes from January 2000 to September 2021.
Review methods: Paired team members independently screened search results, serially abstracted data, assessed risk of bias, and graded strength of evidence (SOE) using standard methods for observational studies.
Results: We included 82 quantitative observational studies and 16 qualitative studies, with 49 studies comparing outcomes of WIC participants with WIC-eligible non-participants. WIC prenatal participation was associated with lower risk of three outcomes: preterm delivery (moderate SOE), low birth weight (moderate SOE), and infant mortality (moderate SOE). Prenatal WIC participation was associated with better maternal diet quality (low SOE), lower risk of inadequate gestational weight gain (low SOE), lower alcohol use in pregnancy (low SOE), and no difference in smoking (low SOE). Maternal WIC participation was associated with increased child preventive care and immunizations (each low SOE), and higher cognitive scores for children (low SOE). Child WIC participation was associated with better diet quality (moderate SOE), and greater intakes of 100 percent fruit juice, whole grain cereals, and age-appropriate milk (moderate SOE). Household WIC participation was associated with greater purchasing of healthy food groups (moderate SOE). Maternal WIC participation was not associated with breastfeeding initiation (moderate SOE). The evidence was insufficient for other outcomes related to maternal health and child growth. The evidence generally was insufficient on how WIC participation affects outcomes across subgroups.
Conclusions: Maternal WIC participation was associated with improved birth outcomes, lower infant mortality, and better child cognitive development. WIC participation was associated with purchasing healthier foods and with improved diets for pregnant women and children. More research is needed on maternal health outcomes; food security; child growth, development, and academic achievement; and effectiveness of WIC in all segments of the eligible population.