ABSTRACT: To determine whether group prenatal care improves pregnancy outcomes, psychosocial function, and patient satisfaction and to examine potential cost differences.A multisite randomized controlled trial was conducted at two university-affiliated hospital prenatal clinics. Pregnant women aged 14-25 years (n=1,047) were randomly assigned to either standard or group care. Women with medical conditions requiring individualized care were excluded from randomization. Group participants received care in a group setting with women having the same expected delivery month. Timing and content of visits followed obstetric guidelines from week 18 through delivery. Each 2-hour prenatal care session included physical assessment, education and skills building, and support through facilitated group discussion. Structured interviews were conducted at study entry, during the third trimester, and postpartum.Mean age of participants was 20.4 years; 80% were African American. Using intent-to-treat analyses, women assigned to group care were significantly less likely to have preterm births compared with those in standard care: 9.8% compared with 13.8%, with no differences in age, parity, education, or income between study conditions. This is equivalent to a risk reduction of 33% (odds ratio 0.67, 95% confidence interval 0.44-0.99, P=.045), or 40 per 1,000 births. Effects were strengthened for African-American women: 10.0% compared with 15.8% (odds ratio 0.59, 95% confidence interval 0.38-0.92, P=.02). Women in group sessions were less likely to have suboptimal prenatal care (P<.01), had significantly better prenatal knowledge (P<.001), felt more ready for labor and delivery (P<.001), and had greater satisfaction with care (P<.001). Breastfeeding initiation was higher in group care: 66.5% compared with 54.6%, P<.001. There were no differences in birth weight nor in costs associated with prenatal care or delivery.Group prenatal care resulted in equal or improved perinatal outcomes at no added cost.ClinicalTrials.gov, www.clinicaltrials.gov, NCT00271960I.