Variations in the use of cesarean delivery for dystocia: lessons about the source of care.

Aggregate data show variations in the use of cesarean delivery according to the source of care, which suggests that rising cesarean rates are at least in part attributable to nonmedical factors. In the research presented here, the likelihood of cesarean delivery is examined for low-risk, primiparous women with physicians who practice in a single hospital but are from three practice organizations--a health maintenance organization (HMO), private practice, and a hospital clinic--while controlling for a wide spectrum of clinical factors. Maternal age was found to be a dominant factor in determining the decision for a cesarean delivery, independent of clinical risk and physicians' practice organization. Only among women in their optimal childbearing years (25 to 29 years) was having an HMO physician associated with a lower likelihood of cesarean delivery. The authors conclude that lowering the primary cesarean rate in the 1990's may require more reeducation and clinical policy formulation, with particular attention being paid to maternal age, and less reorganization of services than the aggregate data suggests.