Prenatal WIC Participation Is Associated with Gestational Weight Gain: A Secondary Analysis of United States Birth Records.

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides breastfeeding support, nutritious supplemental foods, referrals to health care and social services, and nutrition counseling to eligible pregnant women. Evidence on maternal weight outcomes associated with prenatal WIC participation remains sparse.

OBJECTIVES

This study aims to estimate the association between prenatal WIC participation and gestational weight gain (GWG).

METHODS

Birth records data from women eligible for WIC during pregnancy (defined as delivery paid with Medicaid) and of reproductive age, who gave birth to a singleton, live birth, at a hospital in the United States in 2023 were used. Reception of WIC benefits during pregnancy, maternal prepregnancy weight and height, and weight at delivery were reported in the birth records. GWG (weight at delivery minus prepregnancy weight) was standardized for gestational age by calculating gestational age-specific z-scores (GWG z-scores) from prepregnancy-BMI-class-specific references, and categorized into tertiles (low, middle, high). GWG rate (pounds gained/per week during the 2nd and 3rd trimesters) was categorized as slow, adequate, or accelerated. We used propensity scores (PS) weighting to create a balanced comparison group of WIC-eligible non-WIC-participant mothers. Using PS-weighted log binomial regression, we estimated risk ratios (RR) and 95% confidence intervals (CIs) for high/accelerated and low/slow (compared with middle/adequate GWG as reference) GWG associated with prenatal WIC participation.

RESULTS

We analyzed 1,318,604 pregnancies. Prenatal WIC participation was associated with a small reduction in risk of low GWG z-score (RR = 0.981, 95% CI: 0.977, 0.985; P < 0.0001) and slow GWG rate (RR = 0.992, 95% CI: 0.988, 0.995; P < 0.0001). No significant association was detected for prenatal WIC participation and high GWG z-score (RR = 1.003, 95% CI: 0.999, 1.006; P = 0.18), whereas a small increase in risk of accelerated GWG rate (RR = 1.004, 95% CI: 1.002, 1.006; P < 0.0001) was observed.

CONCLUSIONS

Prenatal WIC participation provided support to modestly reduce low weight gain among WIC-eligible United States women, which may have limited clinical implications.