tiple births, births to older women, or changes in medical practice such as induction of labor or cesarean sections before full gestation (Kramer, 1998; Ventura et al., 1999). Birth outcomes in the United States have behaved less like indicators of poor health care and health behaviors, and more like indicators of deeper disparities among women of different social classes and ethnicities (Collins et al., 1997; O'Campo et al., 1997; Roberts, 1997; Johnson et al., 1999). The lack of improvement in indicators of the health of babies at birth is discouraging to public health professionals, but comes as no surprise to social and behavioral scientists.
Public health practice has not fully embraced the contributions that social science and behavioral research have to offer in the design of programs and policies for maternal and infant health (Mechanic, 1995; Grason et al., 1999; Hogue, 1999). The public health model for a healthy start in life is broader than the medical model and addresses disparities in health education, nutrition, and psychosocial conditions of families (Bennett and Kotelchuck, 1997). Public health professionals have long recognized the need to ameliorate effects of social policies that discriminate against economically and ethnically vulnerable populations (Aday, 1993). Public health programs for pregnant women have not had measurable effects on the country's poor pregnancy outcomes in recent years and have had limited effects on infant mortality (Willinger et al., 1998; U.S. Department of Health and Human Services, 1999). To have larger effects on maternal and infant health, innovative programs and policies need to address social, economic, cultural, political, and psychological antecedents of disparities.