Hepatitis B infection in pregnancy: Essentials of antiviral therapy and immunoprophylaxis
Highly contagious, hepatitis B infection may cause serious complications in both the pregnant woman and her neonate. An expert explains which laboratory tests to order and when, as well as diagnosis and treatment approaches for the mother and neonate.
Maternal antiviral therapy
As noted above, neonatal immunoprophylaxis is 85% to 95% effective in preventing perinatal transmission of hepatitis B infection. Failures of prophylaxis are primarily due to antenatal transmission in patients who have exceptionally high viral loads. Several cutoffs have been used to define “high viral load,” including greater than 1 to 2 million copies/mL and a hepatitis B DNA concentration greater than 200,000 IU/mL. There is not a perfect consensus on the appropriate cutoff.
In essence, 2 different approaches have been tried to further reduce the risk of perinatal transmission in these high-risk patients.8 The first major initiative was administration of HBIG (100–200 IU) intramuscularly to the patient at 28, 32, and 36 weeks. The outcomes with this approach have been inconsistent, due, at least in part, to varying doses of the agent and various cutoffs for defining “high risk,” and this intervention is no longer recommended.1,2
The second major approach is administration of specific antiviral drugs to the mother during the third trimester. The first agent widely used in clinical practice was lamivudine. In a systematic review and meta-analysis, Shi and colleagues reported that, in infants whose mothers received lamivudine plus conventional neonatal immunuprophylaxis, the risk of perinatal infection was significantly reduced compared with infants who received only immunoprophylaxis.9
Although lamivudine is effective, there is considerable concern about the rapid development of viral resistance to the medication. Accordingly, most attention today is focused on the use of tenofovir to prevent perinatal transmission.
In an important early investigation, Pan and colleagues reported the results of a randomized controlled trial conducted in China in women with a hepatitis B DNA concentration greater than 200,000 IU/mL (viral load > 1,120,000 copies/mL).10 Patients also were positive for the e antigen. Ninety-two patients were assigned to tenofovir disoproxil fumarate (TDF), 300 mg daily, from 30 to 32 weeks until postpartum week 4 plus conventional neonatal immunoprophylaxis, and 100 patients were assigned to immunoprophylaxis alone. In the intention-to-treat analysis, 18 neonates in the control group were infected compared with 5 in the treatment group (P = .007). In the per-protocol analysis, 7 neonates in the control group were infected compared with 0 in the treatment group (P = .01). No clinically significant adverse maternal or neonatal effects occurred in the treatment group.
Subsequently, Jourdain and colleagues reported a multicenter, double-blind trial conducted in 17 public health hospitals in Thailand.11 TDF (300 mg daily) or placebo was administered from 28 weeks’ gestation until 8 weeks postpartum. Patients in both arms of the study were positive for the e antigen; 87% to 90% of the patients had a serum hepatitis B DNA concentration greater than 200,000 IU/mL.Following birth, infants in both groups received an injection of HBIG and then 4 doses of hepatitis B vaccine (0, 1, 2, 4, and 6 months). Both the HBIG and hepatitis B vaccine were administered very promptly after birth (median time, 1.2–1.3 hours).
At 6 months after delivery, 2% of infants in the placebo group (3 of 147) were HBsAg-positive compared with none of the infants in the treatment arm.11 No serious adverse effects occurred in infants in the TDF group. This difference in outcome was not statistically significant, but the overall rate of infection was so low in both groups that the sample size was definitely too small to exclude a type 2 statistical error. Moreover, the fourth dose of neonatal hepatitis B vaccine may have contributed to the surprisingly low rate of perinatal transmission. Of note, the serum hepatitis B DNA concentration in the TDF group declined from a mean of 7.6 log10 IU/mL to a mean of 4.0 log10 IU/mL at delivery.
In the most recent report, Wang and colleagues reported the results of a prospective cohort study in patients with a hepatitis B virus DNA concentration greater than 200,000 IU/mL.12 Beginning at either 24 or 32 weeks, patients were assigned to treatment with either oral TDF (300 mg daily) or oral telbivudine (LdT, 600 mg daily). The medications were continued for 4 weeks postpartum. In the intention-to-treat analysis, the rates of perinatal transmission were comparable, 1.5% versus 1.8%. In the per-protocol analysis, no infants in either group were infected. However, the predelivery decline in hepatitis Bvirus DNA concentration was greater in the TDF group. The ALT elevation rate was also lower in the TDF group. Patients in the LdT group had fewer problems with anorexia but more instances of arthralgia compared with those in the TDF group.
Based primarily on these 3 investigations, I recommend that all infected patients with a hepatitis B DNA concentration greater than 200,000 IU/mL or a viral load greater than 1,120,000 million copies/mL receive oral TDF, 300 mg daily, from 28 weeks until at least 4 to 8 weeks postpartum. The decision about duration of postpartum treatment should be made in consultation with an infectious disease specialist or hepatologist.
Case studies resolved
CASE 1 No protective level of surface antibody
This patient should promptly receive a single booster dose of the hepatitis B vaccine. The vaccine is an inactivated agent and is safe for administration at any time in pregnancy. Following delivery and prior to discharge from the hospital, the neonate should receive the first dose of the hepatitis B vaccine. A second dose should be administered 1 month later, and a third dose should be administered 6 months after the first dose.
CASE 2 Mother is seropositive for HBsAg
This patient should be tested immediately for HIV infection and hepatitis C and D. The hepatitis B viral genotype should be determined. She also should have a panel of liver function tests. If any of these tests are abnormal, a coagulation profile should be obtained to be certain that the patient is not at risk for a coagulopathy. Near the end of the second trimester, a hepatitis B viral load should be obtained. If the viral DNA concentration is greater than 200,000 IU/mLor a viral load greater than 1,120,000 million copies/mL, the patient should be treated with tenofovir, 300 mg daily, from week 28 until at least 4 weeks after delivery. The neonate should receive an injection of HBIG within 12 hours of birth and the first dose of the hepatitis B vaccine prior to discharge from the hospital. Two additional doses of the vaccine should be administered 1 and 6 months later. ●
