Obstetrics and gynecology has been transformed from a fee-for-service, unmanaged system to a prepaid managed system. This change poses significant ethical challenges, which we address. We show that obstetrician-gynecologists and medical institutions are moral co-fiduciaries of female and pregnant patients, that the obstetrician-gynecologist should be economically disciplined without capitulating to managed care, and that managed care organizations have an obligation to support the medical education and research from which they benefit.