Differences in primary cesarean birth rates between a maternity center staffed by certified nurse-midwives (CNM) with physician backup on the premises and a university teaching hospital staffed by resident and attending physicians were studied. The study sample included 796 and 804 women, similar in demographics, who received their prenatal and intrapartum care in the respective sites in 1977 and 1978. Study results indicate a significantly lower rate of primary cesarean birth at the maternity center than at the university hospital that was independent of institutional differences in the indications for abdominal delivery. Although cesarean birth was related to contracted pelvis (at labor), fetal malepresentation, and placental bleeding at both institutions, it was significantly associated with preeclampsia, primiparity, fetal distress, and maternal age only at the university hospital. There were no noteworthy differences in pregnancy outcomes for women delivered vaginally or by cesarean, except for more newborns with low Apgar scores among primary cesarean births at the university hospital A likely explanation for these findings is differing labor and delivery management styles between the providers of care at the two institutions.