Group prenatal care and improved birth outcomes: Results from a type 1 hybrid effectiveness-implementation study.

To compare birth outcomes for patients receiving Expect With Me (EWM) group prenatal care or individual care only, we conducted a type 1 hybrid effectiveness-implementation trial (Detroit and Nashville, 2014-2016). Participants entered care <24 weeks gestation, had singleton pregnancy, and no prior preterm birth (N = 2402). Mean participant age was 27.1 (SD = 5.77); 49.5% were Black; 15.3% were Latina; 59.7% publicly insured. Average treatment effect of EWM compared to individual care only was estimated using augmented inverse probability weighting (AIPW). This doubly-robust analytic method produces estimates of causal association between treatment and outcome in the absence of randomization. AIPW was effective at creating equivalent groups for potential confounders. Compared to those receiving individual care only, EWM patients did significantly better on three of four primary outcomes: lower risk of infants born preterm (<37 weeks gestation; 6.4% vs. 15.1%, risk ratio (RR) 0.42, 95% Confidence Interval (CI) 0.29, 0.54), low birthweight (<2500 g; 4.3% vs. 11.6%, RR 0.37, 95% CI 0.24, 0.49), and admission to NICU (9.4% vs. 14.6%, RR 0.64, 95% CI 0.49, 0.78). There was no difference in small for gestational age (<10% percentile of weight for gestational age). EWM patients attended a mean of 5.9 group visits (SD = 2.7); 70% attended ≥5 group visits. Post-hoc analyses indicated EWM patients utilizing the integrated information technology platform had lower risk for low birthweight infants (RR 0.47, 95% CI 0.24, 0.86) than non-users. Future research is needed to understand mechanisms by which group prenatal care improves outcomes, best practices for implementation, and health systems savings. Trial registration: ClinicalTrials.govNCT02169024.