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Mothers enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) may experience improved birth outcomes and a lower risk of infant mortality, according to a systematic review.

Women who participated in WIC had reduced risks of preterm birth (10% to 15%) and low birthweight (11% to 24%), reported S. Michelle Ogunwole, MD, PhD, of Johns Hopkins University School of Medicine, and colleagues.

WIC participation was also associated with a 14% to 40% reduced risk of infant mortality, the researchers reported in .

While the strength of the evidence that showed the reduced risk of infant mortality was rated as moderate, indicating that the conclusions could be strengthened with further data, the findings "still underscore the importance of WIC as a part of the country's public health infrastructure," the investigators wrote.

They also identified a few studies that showed differences in associations between WIC participation and adverse birth outcomes as well as infant mortality by race and ethnicity, with larger risk reductions noted among Black women.

"More evidence is needed to evaluate whether WIC participation may provide differential benefits by race and ethnicity," the researchers wrote. "This is important, as maternal mortality, morbidity, and birth and neonatal outcomes are pressing public health issues characterized by important income, racial, and ethnic disparities."

WIC was created in 1974 to serve low-income women and their children younger than 5 years old, providing nutrition and breastfeeding education, referrals to medical providers and social services, and support for high-risk pregnancies. In 2009, the WIC food package was changed to align with recommendations put forth by the National Academies of Sciences, Engineering and Medicine to reduce diet-related chronic illness.

Ogunwole and co-authors conducted the systematic review as a part of a larger evidence report commissioned by the U.S. Department of Agriculture to examine the most recent evidence on the association between WIC participation and maternal and health outcomes. The analysis included studies published between January 2009 and April 2022.

The researchers identified 20 observational studies, 19 of which reported direct evidence. There were seven cohort studies, 11 cross-sectional studies, one case-control study, and a study evaluating the 2009 food package change that provided indirect evidence on birth outcomes.

Ogunwole and colleagues found moderate strength of evidence that WIC participation was associated with a reduced risk of preterm birth and low birthweight.

Three studies provided direct evidence on the relationship between WIC participation and preterm birth. One large national cohort study of 11 million mothers that took place between 2011 and 2017 showed that mothers enrolled in WIC had a 12% reduced risk of preterm delivery (0.88, 95% CI 0.86-0.87).

Additionally, the researchers concluded that WIC participation was associated with lower odds of low birthweight based on evidence from three studies with consistent findings. For example, one retrospective cohort study of more than 200,000 participants found that mothers enrolled in WIC had a nearly 20% lower risk of having a low birthweight infant (hazard ratio 0.81, 95% CI 0.69-0.97).

Two studies provided direct evidence on infant mortality, which was defined as death of an infant less than a year old. One large national cohort study reported 16% lower odds of infant mortality among mothers enrolled in WIC (adjusted OR 0.84, 95% CI 0.83-0.86), and an older study of nearly 3,000 infants based in Puerto Rico also confirmed these findings.

Ogunwole and co-authors said their results highlighted several knowledge gaps regarding WIC's impact on health outcomes. For example, there was no direct evidence describing the association between WIC and maternal morbidity and mortality, and there was only low-quality evidence about gestational weight gain. There was also insufficient evidence on the relationship between WIC participation and childhood health outcomes, such as receipt of immunizations.

Study limitations, the team said, included that the findings are based on data from observational studies, and that there was a high potential for selection bias, since people included in the study chose whether or not to participate in WIC. Participation status was also self-reported in most of the studies reviewed, the researchers noted.

"Overall, this review highlights the need for higher quality evidence on the association of maternal and child WIC participation with maternal, infant, and child health outcomes," Ogunwole and colleagues wrote. They called for further study of participant characteristics, as well as the timing and duration of WIC participation, "given the potential for WIC to reduce disparities in maternal, infant, and child health."

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