This report reviews the literature on the process and outcomes of prenatal care for the purpose of developing criteria by which such care could be assessed. The report includes the final set of criteria agreed upon by a Working Group of the HMO Quality of Care Consortium that was used in a study of the quality of prenatal care conducted in six health maintenance organizations. The key outcomes affected by prenatal care are: perinatal mortality, birthweight, preterm delivery, neonatal intensive care admissions, and neonatal and maternal complications. The report recommends focusing on the processes of care because adverse outcomes are rare. The prenatal care processes reviewed include: timing and frequency of visits, risk assessment, determination of gestational age, nutrition counseling, substance abuse detection and counseling, screening for infections, sexually transmitted diseases, and congenital fetal disorders, and identifying and managing common pregnancy complications. The report also summarizes studies on patient characteristics that are associated with variations in both processes and outcomes and the cost-effectiveness of prenatal care.