Have WIC revisions improved maternal and infant health?

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In October 2009, 30 years after its introduction, the Special Supplemental Nutritional Program for Women, Infants, and Children (WIC) implemented major revisions to improve nutritional content. A recent study, published in JAMA Pediatrics, investigated whether the revised food package improved perinatal and birth outcomes among recipients.

The quasi-experimental difference-in-differences analysis compared WIC recipients before and after the package revisions. The major revision to the package was including more whole grains, fruits, vegetables, and low-fat milk. Non-WIC recipients were included in the study as a control group and multivariable linear regression was applied to adjust for sociodemographic covariates. The study used linked birth certificate and hospital discharge data from California from January 2007 to December 2012. 

Maternal outcomes relevant to the study included a diagnosis of preeclampsia or gestational diabetes. Maternal weight was also recorded, and the authors calculated whether the mother gained more or less weight, or was within recommended gestational weight gain according to guidelines from the Institute of Medicine (now the National Academy of Medicine). Relevant infant outcomes included a z score for birth weight, weeks of gestation at delivery, and hospitalizations. 

The sample included nearly 2 million infants (N=1,569,045 WIC recipients [821,878 births born before revision; 747,167 births born after revision]) born to nearly 2.5 million mothers. Overall, 68.1% of WIC recipients were Hispanic, versus 26.0% of non-recipients. In terms of education, 25.2% of WIC recipients had more than a high school education compared with 72.9% of non-recipients. Although maternal health was similar for both recipients and non-recipients, the health of WIC- recipient infants was worse for several outcomes, including a lower birth weight z score (-0.002 vs 0.05), a higher proportion with small for gestational age (SGA) birth weight (8.9% vs 8.0%), a longer-than-expected admission at birth (11.1% vs 9.6%), and more readmission in the first year of life (11.1% vs 8.7%).

The revised WIC food package was found to be effective in reducing negative maternal outcomes. Maternal preeclampsia rates were lower following the revision (-0.7% points; 95% CI, -0.8 to -0.4) and gestational gain of more weight than recommended was reduced (-3.2% points; 95% CI -3.6 to -2.7). Furthermore, there was also an increased likelihood of as-recommended (2.3% points; 95% CI, 1.8 to 2.8) and less-than-recommended gestational weight gain (0.9% points; 95% CI; 0.5 to 1.2) in the post-revision cohort. Gestational age was also slightly longer in the post-revision group (0.2 weeks; 95% CI 0.001 to 0.034).

The revision was also beneficial for infants. An increased likelihood of birth weight appropriate for gestational age was seen following the revision (0.9% points; 95% CI 0.5 to 1.3). The authors note that while birth weight was reduced (-0.009 SDs; 95% CI, -0.016 to -0.001), this reduction was also supplemented with reductions in SGA (-0.045% points; 95% CI-0.7 to -0.1), large for gestational age (-0.5% points; 95% CI -0.8 to -0.2) and low-birth-weight infants (-0.2% points; 95% CI -0.4 to -0.004, which may indicate that the revised food package improved distributions of birth weight. 

The authors believe that the revisions to the WIC food package were successful in their goal of improving maternal and infant health. These findings also indicate that the WIC program may play an important role in reducing some of the health disparities between women and children at lower socioeconomic levels, and the program is reducing these disparities at a critical period in the lives of high-risk women and children.