In this trial, 200 mothers, who were positive for hepatitis-B e antigen (HBeAg) and who had hepatitis-B virus (HBV) DNA level >200,000 IU/mL, were randomly assigned to receive usual care without antiviral therapy or to receive tenofovir (TDF) at an oral dose of 300 mg/d from 30 to 32 weeks of gestation until postpartum week 4; the participants were followed until postpartum week 28. All the infants received immunoprophylaxis. The primary outcomes were the rates of mother-to-child transmission and birth defects. The secondary outcomes were the safety of TDF, the percentage of mothers with an HBV DNA level of <200,000 IU/mL at delivery, and loss or seroconversion of HBeAg or hepatitis B surface antigen at postpartum week 28. At delivery, 68% of the mothers in the TDF group (66 of 97 women), as compared with 2% in the control group (2 of 100), had an HBV DNA level <200,000 IU/mL. At postpartum week 28, the rate of mother-to-child transmission was significantly lower in the TDF group than in the control group, both in the intention-to-treat analysis (5% vs. 18%, P=0.007) and the per-protocol analysis (0 vs. 7%, P=0.01). The maternal and infant safety profiles were similar in the TDF group and the control group, including birth defect rates (2% vs. 1%, P=1.00), although more mothers in the TDF group had an increase in the creatine kinase level. After the discontinuation of TDF, alanine aminotransferase elevations above the normal range occurred more frequently in mothers in the TDF group than in those in the control group (45% vs. 30%, P=0.03). The authors concluded that in HBeAg-positive mothers with an HBV DNA level >200,000 IU/mL during the third trimester, the rate of mother-to-child transmission was lower among those who received TDF therapy than among those who received usual care without antiviral therapy.

Relevance: Perinatal transmission of Hepatitis B infection is associated with unpleasant consequences for individuals as well as the society – the former because transmission from mothers with active viral replication is associated with high probability of chronicity in the affected offspring, and the latter because it contributes to the pool of chronic carriers in the community. The impact of perinatal transmission has been significantly mitigated by the strategy of combined passive (immunoglobulin) and active (vaccination) immunization [1]. However, it is reported that these measures are unsuccessful in cases with high load of actively replicating viruses (HBeAg positive women with HBV DNA >1 million copies/mL) [2,3]. In such situations, there is emerging data that antiviral agents such as telbivudine administered to pregnant women may be efficacious [4], well tolerated [5] as well as cost-effective [6]. Researchers have also tried other antiviral agents including tenofovir [7]; however robust evidence is lacking. Pan, et al. [8] sought to address this gap through a randomized controlled trial (RCT) comparing tenofovir (Intervention) vs usual care (Comparison) for preventing perinatal transmission of Hepatitis B (Outcome) from mothers with high viral load (Population). Table I presents the trial outline.

Table I Outline of the Trial

Critical appraisal: The RCT was well designed and conducted as planned. Table II presents a summary of critical appraisal of methodological characteristics using the Cochrane Risk of Bias tool [9]. Overall, the trial had moderate risk-of-bias. The trial included several refinements worthy of mention. Follow-up till 28 weeks postpartum is fairly standard in such trials. The investigators attempted to measure adherence to therapy by counting pills at follow-up visits (although the data are not presented). Follow-up visits were fairly frequent (every 4 weeks before delivery) and thereafter at 4, 12, 24 and 28 weeks postpartum.

Table II Methodological Appraisal of the Trial

The investigators also attempted to monitor development of antiviral resistance by genome sequencing of HBV in case of breakthrough or early discontinuation of treatment. Various terminologies associated with the trial were strictly defined and objective criteria used where feasible. The authors also conducted several post hoc analyses and presented them in Supplementary tables. Data were analyzed by intention-to-treat, although the principle that all randomized participants should be included in the analysis (irrespective of whether or not they receive the intended treatment) was not strictly followed. The investigators did not pursue statistical modelling with best-case and worst-case scenarios.

Extendibility: India qualifies as a low intermediate endemicity country based on chronic HBV infection prevalence in the general population ranging from 2-4% [10,11]. Current data indicate that less than 1-1.5% pregnant women are chronic carriers [12-14]. The precise contribution of perinatal/vertical transmission the pool of chronic carriers in India is unclear. This is in contrast to China which is regarded as a highly endemic country with >8% chronic carrier rate [10], and 5-10% of the chronic carrier pool is derived by vertical transmission [15]. For these reasons, the decision to treat eligible pregnant women with antiviral agents, in our setting has to be individualized rather than empiric [16].

Conclusion: This well-designed multicentric randomized trial suggests that in pregnant women with high probability of transmitting hepatitis B vertically, tenofovir initiated during the third trimester and continued beyond delivery could be a useful intervention to reduce perinatal transmission.

Funding: None; Competing interest: None stated.

Joseph L Mathew

1. Pande C, Sarin SK, Patra S, Kumar A, Mishra S, Srivastava S, et al. Hepatitis B vaccination with or without hepatitis B immunoglobulin at birth to babies born of HBsAg-positive mothers revents overt HBV transmission but may not prevent occult HBV infection in babies: a randomized controlled trial. J Viral Hepat. 2013;20:801-10.

2. Wang C, Wang C, Jia ZF, Wu X, Wen SM, Kong F, et al. Protective effect of an improved immunization practice of mother-to-infant transmission of hepatitis B virus and risk factors associated with immunoprophylaxis failure. Medicine (Baltimore). 2016;95:e4390.

3. Li J. Nucleos(t)ide antiviral agents for preventing mother-to-child transmission of hepatitis B virus: an interpretation of relevant international guidelines). Zhonghua Gan Zang Bing Za Zhi. 2016;24:143-6.

4. Sheng QJ, Ding Y, Li BJ, Bai H, Zhang C, Han C, et al. Telbivudine for prevention of perinatal transmission in pregnant women infected with hepatitis B virus in immune-tolerant phase: a study of efficacy and safety of drug withdrawal. Zhonghua Gan Zang Bing Za Zhi. 2016;24:258-64.

5. Deng Y, Wu W, Zhang D, Hu P, Kang J, Yang Y, Zeng W. The safety of telbivudine in preventing mother-to-infant transmission of hepatitis B virus in pregnant women after discontinuation). Zhonghua Gan Zang Bing Za Zhi. 2015; 23:586-9.

6. Wang W, Wang J, Dang S, Zhuang G. Cost-effectiveness of antiviral therapy during late pregnancy to prevent perinatal transmission of hepatitis B virus. PeerJ. 2016;24:e1709.

7. Hu YH, Liu M, Yi W, Cao YJ, Cai HD. Tenofovir rescue therapy in pregnant females with chronic hepatitis B. World J Gastroenterol. 2015;21:2504-9.

8. Pan CQ, Duan Z, Dai E, Zhang S, Han G, Wang Y, et al. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016;374:2324-34.

9. Cochrane Risk of Bias Tool (modified) for quality assessment of randomize controlled trials. Available from: http://www.tc.umn.edu/~msrg/caseCATdoc/rct.crit.pdf. Accessed September 15, 2016.

10. Averoff F. Hepatitis B. Available from: http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-diseases-related-to-travel/hepatitis-b.Accessed September 15, 2016.

11. Puri P. Tackling the hepatitis B disease burden　in India. J Clin Exp Hepatol. 2014;4:312-9.

12. Dwivedi M, Misra SP, Misra V, Pandey A, Pant S, Singh R, Verma M. Seroprevalence of hepatitis B infection during pregnancy and risk of perinatal transmission. Indian J Gastroenterol. 2011;30:66-71.

13. Trehanpati N, Hissar S, Shrivastav S, Sarin SK. Immunological mechanisms of hepatitis B virus persis-tence in newborns. Indian J Med Res 2013;138:700-10.

14. Alexander AM, Prasad JH, Abraham P, Fletcher J, Muliyil J, Balraj V. Evaluation of a programme for prevention of vertical transmission of hepatitis B in a rural block in southern India. Indian J Med Res. 2013;137:356-62.

15. Ren Y, Guo Y, Feng L, Li T, Du Y. Controversy and Strategies Exploration in Blocking Mother-to-Child Transmission of Hepatitis B. Int Rev Immunol. 2016;35:249-259.

16. Kar P, Mishra S. Management of hepatitis B during pregnancy. Expert Opin Pharmacotherap. 2016;17:301-10.

In their study, Pan, et al. [3] included 200 HBeAg positive women with high viral load (>200,000 IU/mL). The maternal to child transmission was significantly less in the tenofovir (TDF) group as compared to the control group in both intention-to-treat analysis (5% vs 18%) and per protocol analysis (0% vs 7%) at 28 weeks postpartum and fetal safety profile was similar in both groups.

Factors to consider drug therapy for routine use in prevention of mother-to-child transmission include risk of postpartum flares on stopping treatment, drug resistance and lack of long term safety data. In the present study, there was a significant elevation of alanine aminotransferase levels after discontinuation of TDF and 89% had a viral rebound on stopping treatment at 4 weeks postpartum. Drug resistance is reported to be low with TDF as compared to Lamuvidine, and in this trial all five women with viral rebound showed no genotypic mutation.

The birth defects rate is 2.7% with Tenofovir; however, the defects have only been identified at birth and there is a short follow-up. Tenofovir was given to women in the third trimester; hence teratogenic potential of the drug cannot be interpreted in the study. One stillbirth and neonatal death was reported in the TDF group as compared to none in the controls but the reasons cited were not linked to TDF. Limited data is available on maternal side effects like bone remodelling and osteoporosis; maternal creatinine kinase levels were elevated in this study and the result was interpreted as clinically non-significant. Another area of contention is optimal duration of continuation of therapy postpartum (4 weeks or 12 weeks) as the drug is excreted in breast milk and safety data on neonates is insufficient. In this study, the women were instructed not to breastfeed for 4 weeks in the treatment group. Besides viral load and HBeAg status, other factors responsible for true immunization failure like maternal cytokine polymorphism and transplacental infection are not eliminated with drug therapy.

Till date, treatment for hepatitis B infection in pregnant women is given routinely for mothers with advanced disease, acute exacerbation or in liver failure where maternal benefits outweigh fetal risks; its routine use to prevent perinatal transmission is not widely accepted. The present study indeed adds to the much needed good quality evidence, but larger trials with a longer follow-up in terms of efficacy, duration of treatment and maternal and fetal safety are required for routine practice. There is also a research gap to determine the optimal threshold of HBV DNA for antiviral therapy.

Funding: None; Competing interest: None stated.

Bindiya Gupta

1. McMahon BJ, Alward WLM, Hall DB,　Heyward WL,　Bender TR,　Francis DP, et al. Acute hepatitis B virus infection: relation of age to the clinical expression of disease and subsequent development of the carrier state. J　Infect Dis. 1985;151:599-603.

2. Wiseman E, Fraser MA, Holden S, Glass A, Kidson BL, Heron LG, et al. Perinatal transmission of hepatitis B virus: an Australian experience. Med J Aust. 2009;190:489-92.

3. Pan CQ, Duan Z, Dai E, Zhang S, Han G, Wang Y, et al. China Study Group for the Mother-to-Child Transmission of Hepatitis B. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016; 374:2324-34.

Interruption of mother-to-child transmission of hepatitis B virus (HBV) infection is important not only for preventing chronic liver disease and hepatocellular carcinoma in the offspring but also from the perspective of reducing the global burden of chronic liver disease. Vertical transmission of hepatitis B accounts for almost half of the chronic liver disease seen worldwide, and India has the second largest pool of chronic HBV infection despite much lower seroprevalence than China and other Southeast Asian countries (0.9% versus 10-20%) [1].

With current body of evidence, oral tenofovir prophylaxis must be offered to eligible HBsAg-positive pregnant women. This needs strengthening and standardization of laboratory monitoring and management planning. HBV-DNA levels and HBeAg status must be determined at beginning of third trimester in HBsAg-positive pregnant women, and those classified to have high replicative status should be managed at a tertiary care center by a team of hepatologist, obstetrician and neonatologist.

Funding: None; Competing interest: None stated.

1. Trehanpati N, Hissar S, Shrivastav S, Sarin SK. Immunological mechanisms of hepatitis B virus persistence in newborns. Indian J Med Res. 2013;138: 700-10.

2. Schillie S, Walker T, Veselsky S, Crowley S, Dusek C, Lazaroff J, et al. Outcomes of infants born to women infected with hepatitis B. Pediatrics. 2015;135:e1141-7.

3. Pande C, Sarin SK, Patra S, Kumar A, Mishra S, Srivastava S, et al. Hepatitis B vaccination with or without hepatitis B immunoglobulin at birth to babies born of HBsAg-positive mothers prevents overt HBV transmission but may not prevent occult HBV infection in babies: a randomized controlled trial. J Viral Hepat. 2013;20:801-10.

4. Brown RS, McMahon BJ, Lok ASF, Wong JB, Ahmed AT, Mouchli MA, et al. Antiviral therapy in chronic hepatitis B viral infection during pregnancy: A systematic review and meta-analysis. Hepatol Baltim Med. 2016;63:319-33.

5. Sarin SK, Kumar M, Lau GK, Abbas Z, Chan HLY, Chen CJ, et al. Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update. Hepatol Int. 2016;10:1-98.