Maternal HBV linked to cord blood viraemia
In mothers chronically infected with hepatitis B virus (HBV), the presence of HBV DNA and hepatitis B e antigen (HBeAg) in the serum appears to be linked to cord blood viraemia in infants, according to a recent Singapore study.
The study included 92 women who tested positive for hepatitis B surface antigen (HBsAg) and who delivered at the National University Hospital in Singapore. Most (n=65; mean age 32.6±5.0 years) tested negative for HBeAg and most births were done vaginally. Umbilical cord blood (UCB) was collected and used in the quantification of cord blood HBV DNA.
In the HBeAg-negative group, 36 of the 65 cords tested positive for viraemia, yielding a viraemia rate of 0.55. In mothers positive for HBeAg, only five cords were without viraemia, resulting in a corresponding rate of 0.81. HBeAg positivity emerged as a significant risk factor for HBV viraemia in cord blood (relative risk [RR], 1.48; 95 percent CI, 1.11–1.95; p<0.05). [Pediatr Neonatol 2019;doi:10.1016/j.pedneo.2019.01.002]
In terms of maternal serum levels of HBV DNA, the viraemia rate was higher in women with >6 vs <6 log IU/mL (0.90 vs 0.56). The resulting risk of cord blood viraemia was significantly elevated in infants born to mothers with >1×106 IU/mL HBV DNA levels (RR, 1.62; 1.25–2.09; p<0.001).
Moreover, there was a moderate, positive and significant correlation between detectable levels of maternal serum and cord blood HBV DNA, such that a higher antenatal concentration of maternal HBV DNA translated to higher detectable levels of the same marker in infants at birth.
“This study showed that the levels of umbilical cord HBV DNA increased with maternal HBV DNA in the third trimester and correlated to the maternal HBeAg positivity,” said researchers. “However, the overall vertical transmission rate is not increased in our study population even in the presence of UCB viraemia with the current standard HBV immunoprophylaxis regimen.”
Indeed, in a subsequent analysis, they found that there was only one case of vertical transmission in children born to HBeAg-positive mothers. No such instances were reported in HBeAg-negative infants, and both groups had comparable levels of anti-HB titres.
In the single case of vertical transmission, both maternal and umbilical cord concentrations of HBV DNA were greater than 1×105 IU/mL, though no premature breach of amniotic membranes occurred. At 9 months of age, the infant’s serum tested positive for HBV DNA, as detected by polymerase chain reaction.
In comparison, despite detectable HBV DNA in the cord blood, all the other children were able to mount an immune response and reach anti-HB antibody levels >10 IU/L.
“Vertical transmission of HBV is thought to occur perinatally, hence the significant fall in infection rates with early combined active and passive immunization,” researchers explained, adding that high maternal HBV loads tend to result in immunoprophylaxis failure. [Vaccine 1997;15:1624]
“In these cases, the use of antiviral therapy during the third trimester may aid in reducing perinatal transmission,” they noted. [Semin Liver Dis 2013;33:138-146]