***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: 447 infants , born to mothers positive for hepatitis B e antigen and hepatitis B surface antigen ( HBsAg ) , received hepatitis B immunisation . A higher rate of hepatitis B virus ( HBV ) infection was found at birth in infants delivered vaginally ( 96/385 , 24.9 % ) than in infants delivered by caesarean section  ( 6/62 , less than 10 % ) . At birth , serum HBV-DNA was detected in 13 of 67 infants delivered vaginally , but in none of 30 infants delivered by caesarean section . Caesarean section combined with hepatitis B immunisation is advisable in infants of mothers who are chronic HBsAg carriers with high serum HBV-DNA levels Methods for combining data from several studies exist and appear to be quite useful . None satisfactorily addresses the question of what studies should be combined . This issue is the most serious method ological limitation . Even studies with statistically significant interaction might still be combined if the effect were in the same direction . Thus , substantial scientific input is required as to what criteria must be met by each potential study . Much can be learned from combining or pooling data but it must be done cautiously . Pooling exercises do not replace well design ed prospect i ve clinical trials . Efforts for establishing basic design criteria to allow for multicentre and multicountry trials to be more easily combined might be useful . BACKGROUND & AIMS Telbivudine reduces hepatitis B virus ( HBV ) DNA and normalizes levels of alanine aminotransferase ( ALT ) in patients with chronic hepatitis B ( CHB ) . We investigated its use in preventing vertical transmission . METHODS We performed an open-label , prospect i ve study of 88 hepatitis B ( HB ) e antigen (HBeAg)-positive pregnant women with CHB , levels of HBV DNA > 6 log(10 ) copies/mL , and increased levels of ALT . Women were given telbivudine ( n = 53 ) starting in the 2nd or 3rd trimester , or no treatment ( controls , n = 35 ) and followed until postpartum week ( PPW ) 28 . All infants received st and ard immunoprophylaxis after birth . RESULTS At 28 weeks , none of the infants whose mothers received telbivudine had immunoprophylaxis failure , whereas 8.6 % of the infants of control mothers did ( P = .029 ) . There were no differences between groups in mothers ' adverse events or infants ' congenital deformities , gestational age , height , and weight , or Apgar scores . At postpartum week 28 , significantly more telbivudine-treated mothers had levels of HBV DNA < 500 copies/mL , normalized levels of ALT , and hepatitis B e antigen seroconversion compared with controls ( 58 % vs none , P < .001 ; 92 % vs 71 % ; P = .008 ; and 15 % vs none ; P < .001 , respectively ) but none had loss of hepatitis B surface antigen .  Telbivudine-treated mothers had no virologic breakthrough ( HBV DNA > 1 log(10 ) increase from < 500 copies/mL ) or discontinuations from adverse events . After delivery , 13/52 patients discontinued telbivudine due to preference . There were no episodes of severe hepatitis ( levels of ALT > 10 times the upper limit of normal ) in either group during 28 weeks of postpartum observation . CONCLUSIONS Women with CHB given telbivudine  during the second or third trimester of pregnancy have reduced rates of perinatal transmission .  Telbivudine produced no adverse events in mothers or infants by 28 weeks BACKGROUND & AIMS In the Asia-Pacific region , perinatal transmission of the hepatitis B virus ( HBV ) is the primary cause of chronic hepatitis B infection . Despite the use of HBIG and HBV vaccination , HBV perinatal transmission ( PT ) occurs in 10 - 30 % of infants born to highly viremic mothers . We evaluated the efficacy and safety of LTD use during late pregnancy in reducing HBV transmission in highly viremic HBeAg+mothers . METHODS Two hundred and twenty-nine HBeAg+HBV DNA levels>1.0 × 10(7 ) copies/ml mothers received telbivudine 600 mg/day from week 20 to 32 of gestation ( n=135 ) or served as untreated controls ( n=94 ) . All infants in both arms received 200 IU of HBIg within 12 h postpartum and recombinant HBV vaccine of 20 μg at 0 , 1 , and 6 months  . HBsAg and HBV DNA results of infants at week 28 were used to determine perinatal transmission rate . All telbivudine treated subjects were registered in the Antiretroviral Pregnancy Registry . RESULTS Telbivudine treatment was associated with a marked reduction in serum HBV DNA and hepatitis B e antigen ( HBeAg ) levels and normalization of elevated ALT levels before delivery . A striking decline of HBV DNA levels started from treatment onset to week 4 , and sustained in a low level since week 12 . Forty-four ( 33 % ) of the 135 telbivudine-treated mothers and none ( 0 % ) of the untreated controls had polymerase chain reaction-undetectable viremia ( DNA<500 copies/ml ) at delivery . Seven months after delivery , the incidence of perinatal transmission was lower in the infants that completed follow-up born to the telbivudine-treated mothers than to the controls ( 0 % vs. 8 % ; p=0.002 ) . HBV DNA levels were only detectable in HBsAg+infants . No significant differences in anti-HBs levels were observed during postnatal follow-up . No serious adverse events were noted in the telbivudine-treated mothers or their infants . CONCLUSIONS Telbivudine used during pregnancy in CHB HBeAg+highly viremic mothers  can safely reduce perinatal HBV transmission . Telbivudine was well-tolerated with no safety concerns in the telbivudine-treated mothers or their infants on short term follow up . These data support the use of telbivudine in this special population BACKGROUND & AIMS Immunoprophylaxis reduces but does not completely eradicate hepatitis B virus ( HBV ) transmission . This prospect i ve study aims at assessing the rate and risk factors of maternally transmitted HBV infection . METHODS We enrolled 303 mother-infant pairs with positive maternal hepatitis B surface antigen ( HBsAg ) under current immunization program . Maternal viral load was determined by a real-time PCR-based assay . The children were tested for HBsAg at 4 - 8 months and /or 1 - 3 years of age . Rates of HBV infection were estimated using a multivariate logistic regression model . RESULTS HBeAg-positive mothers ( 81/303 , 26.7 % ) had higher viral loads than HBeAg-negative mothers ( 7.4 ± 1.9 vs. 2.7 ± 1.4 log10 copies/ml , p<0.0001 ) . Ten children , born to HBeAg-positive mothers with high viral load ( median , 8.4 ; range , 6.5 - 9.5 log₁₀ copies/ml ) , were chronically infected . After adjustment for maternal age , birth type , factors related to maternal-fetal hemorrhage , gestational age , infant gender , birth weight , timeliness of vaccination , and feeding practice , maternal viral load was significantly associated with risk of infection ( adjusted odds ratio for each log₁₀ copy/ml increase , 3.49 ; 95 % confidence interval ( CI ) , 1.63 - 7.48 ; p=0.001 ) . The predictive rates of infection at maternal viral load levels of 7 , 8 , and 9 log₁₀ copies/ml were 6.6 % ( 95 % CI , 0.5 - 12.6 % ; p=0.033 ) , 14.6 % ( 95 % CI , 5.6 - 23.6 % ; p=0.001 ) , and 27.7 % ( 95 % CI , 13.1 - 42.4 % ; p<0.001 ) , respectively . CONCLUSIONS Additional strategies to further reduce transmission should be considered in mothers with a viral load above 7 - 8 log₁₀ copies/ml 
    Output:
    
Subgroup analysis of hepatitis B e-antigen-positive women who underwent Caesarean section did not show a significant reduction in vertical transmission .
DISCUSSION Caesarean section may protect against HBV transmission ; however , convincing benefit could not be demonstrated due to significant study heterogeneity from variable HBIG administration , highlighting the importance of HBIG in HBV prevention .