Hepatitis B during pregnancy presents with unique management issues for both the mother and fetus. These include the effects of HBV on maternal and fetal health, the effects of pregnancy on the course of HBV infection, treatment of HBV during pregnancy, and prevention of perinatal transmission. Prevention of perinatal transmission is an important component of global efforts to reduce the burden of chronic HBV since vertical transmission is responsible for approximately one-half of chronic infection worldwide. (See "Epidemiology, transmission, and prevention of hepatitis B virus infection".)
The risk of developing chronic HBV infection is inversely proportional to the age at time of exposure. The risk is as high as 90 percent in those exposed at birth, while the risk is much lower (about 20 to 30 percent) in those exposed during childhood. Maternal screening programs and universal vaccination have significantly reduced transmission rates. Identification of at-risk mothers permits prophylaxis against transmission, which can reduce transmission rates from 90 percent to as low as 5 to 10 percent. Methods of prophylaxis and risk factors for transmission despite prophylaxis are described further below.
IMPLICATIONS OF HBV INFECTION FOR THE MOTHER
Effect on pregnancy outcomes
Acute HBV — Acute viral hepatitis is the most common cause of jaundice in pregnancy . Other causes include acute liver diseases associated with pregnancy such as acute fatty liver of pregnancy, HELLP, and intrahepatic cholestasis of pregnancy (see appropriate topic reviews).
Acute HBV infection during pregnancy is usually not severe and is not associated with increased mortality or teratogenicity [1,2]. Thus, infection during gestation should not prompt consideration of termination of the pregnancy. However, there have been reports of an increased incidence of low birth weight and prematurity in infants born to mothers with acute HBV infection [2,3]. Furthermore, acute HBV occurring early in the pregnancy has been associated with a 10 percent perinatal transmission rate . Transmission rates significantly increase if acute infection occurs at or near the time of delivery, with rates reported as high as 60 percent .
Treatment of acute infection during pregnancy is mainly supportive. Liver biochemical tests and prothrombin time should be monitored. Antiviral therapy is usually unnecessary, except in women who have acute liver failure or protracted severe hepatitis  (see "Clinical manifestations and natural history of hepatitis B virus infection", section on 'Acute hepatitis'). In this setting, lamivudine (100 mg daily) is a reasonable option since it has been used safely during pregnancy and the anticipated duration of treatment is short . Telbivudine or tenofovir (both considered pregnancy class B drugs by the US Food and Drug Administration [FDA]) are acceptable alternatives. (See 'Antiviral therapy during pregnancy' below.)