Family physicians encounter diagnostic and treatment issues when caring for pregnant women with hepatitis B or C and their newborns. When hepatitis B virus is perinatally acquired, an infant has approximately a 90 percent chance of becoming a chronic carrier and, when chronically infected, has a 15 to 25 percent risk of dying in adulthood from cirrhosis or liver cancer. However, early identification and prophylaxis is 85 to 95 percent effective in reducing the acquisition of perinatal infection. Communication among members of the health care team is important to ensure proper preventive techniques are implemented, and standing hospital orders for hepatitis B testing and prophylaxis can reduce missed opportunities for prevention. All pregnant women should be screened for hepatitis B as part of their routine prenatal evaluation; those with ongoing risk factors should be evaluated again when in labor. Infants of mothers who are positive for hepatitis B surface antigen should receive hepatitis B immune globulin and hepatitis B vaccination within 12 hours of birth, and other infants should receive hepatitis B vaccination before hospital dis- charge. There are no effective measures for preventing perinatal hepatitis C transmission, but transmission rates are less than 10 percent. Perinatally acquired hepatitis C can be diagnosed by detecting hepatitis C virus RNA on two separate occasions between two and six months of age, or by detecting hepatitis C virus antibodies after 15 months of age.