This paper presents the conceptual framework and implementation strategies of a relationship-focused behavioral intervention for pregnant women and their families. The program, PrePare ('Prenatal Parenting'), was designed as a prenatal precursor to the pediatric health care model, Healthy Steps. PrePare includes preventive intervention elements that address parents' universal concerns about pregnancy and parenthood, as well as specific activities to support optimum pregnancy health and reduce high-risk behaviors. As described here, the program is embedded within a large not-for-profit health-maintenance organization (HMO). Delivery of the prenatal component is carried out by Healthy Steps interventionists through three home visits and telephone follow-up during mothers' second and third trimesters of pregnancy. An evaluation of program outcomes is underway. The design compares three groups of families, those who receive PrePare followed by Healthy Steps, Healthy Steps alone and a usual HMO-practice comparison. It is hypothesized that initiating expanded services during the prenatal period will lead to increases in reported patient satisfaction, provider satisfaction and organizational efficiency within the health care delivery system.