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Original Investigation
July 1, 2019

Association of Revised WIC Food Package With Perinatal and Birth Outcomes: A Quasi-Experimental Study

Author Affiliations
  • 1Department of Family & Community Medicine, University of California, San Francisco
  • 2Philip R. Lee Institute for Health Policy Studies, University of California, San Francisco
  • 3California Preterm Birth Initiative, University of California, San Francisco
  • 4Department of Pediatrics, University of California San Diego, La Jolla
  • 5Department of Epidemiology & Biostatistics, University of California, San Francisco
JAMA Pediatr. 2019;173(9):845-852. doi:10.1001/jamapediatrics.2019.1706
Key Points

Question  Did revisions to the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food package in October 2009, which increased access to whole grains, fruits, vegetables, and low-fat milk, result in improvements in maternal or infant health?

Findings  In this quasi-experimental study of 2 897 537 infants, the revised WIC food package was associated with reduced maternal preeclampsia and gestational weight gain as well as improvements in infant gestational age and birth weight.

Meaning  This evaluation of a major US public health program suggests that improving women’s nutrition may be an important target of clinical interventions and health policy.

Abstract

Importance  The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves more than one-quarter of pregnant and postpartum women. In October 2009, the WIC food package underwent revisions to improve nutritional content. No studies have investigated the downstream effects of this revision on maternal and infant health.

Objective  To investigate whether the revised WIC food package improved perinatal and birth outcomes among recipients.

Design, Setting, and Participants  We conducted a quasi-experimental difference-in-differences analysis, comparing WIC recipients (the treatment group) before and after the package revisions while accounting for temporal trends among nonrecipients (the control group). Multivariable linear regressions were adjusted for sociodemographic covariates. This study was conducted using linked birth certificate and hospital discharge data from California from January 2007 to December 2012. Analysis began July 2018.

Exposures  Whether pregnant women received the revised WIC package, which included more whole grains, fruit, vegetables, and low-fat milk.

Main Outcomes and Measures  Measures of maternal and infant health, including maternal preeclampsia, gestational diabetes, and gestational weight gain as well as infant gestational age, birth weight, and hospitalizations.

Results  The sample included 2 897 537 infants born to 2 441 658 mothers. WIC recipients were more likely to be Hispanic, less educated, of greater parity, and younger than nonrecipients. The revised WIC food package was associated with reductions in maternal preeclampsia (−0.6% points; 95% CI, −0.8 to −0.4) and more than recommended gestational weight gain (−3.2% points; 95% CI, −3.6 to −2.7), increased likelihood of as recommended (2.3% points; 95% CI, 1.8 to 2.8) and less than recommended (0.9% points; 95% CI, 0.5 to 1.2) gestational weight gain, and longer gestational age (0.2 weeks; 95% CI, 0.001 to 0.034). Among infants, an increased likelihood of birth weight that was appropriate for gestational age was observed (0.9% points; 95% CI, 0.5 to 1.3). Although birth weight itself was reduced (−0.009 SDs; 95% CI, −0.016 to −0.001), this was accompanied by reductions in small for gestational age (−0.4% 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), suggesting that the revised food package improved distributions of birth weight.

Conclusions and Relevance  The revised WIC food package, intended to improve women’s nutrition during pregnancy, was associated with beneficial impacts on maternal and child health. This suggests that WIC policy may be an important lever to reduce health disparities among high-risk women and children at a critical juncture in the life course.

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