By
Liz Highleyman
Guidelines
recommend that babies born to women with chronic
hepatitis B should receive the first dose of the HBV
vaccine series immediately after birth; anti-HBV antibodies
(hepatitis B immunoglobulin, or HBIG) may also be used. These
steps dramatically reduce the risk of vertical transmission,
but a small proportion of children become infected even with
immuno-prophylaxis.
A.E.
Singh from the University of Alberta and colleagues performed
a case-control study to analyze maternal factors contributing
to mother-to-child HBV transmission to infants receiving adequate
prophylaxis.
The
researchers compared blood samples blood drawn before delivery
from hepatitis B surface antigen (HBsAg) positive mothers
whose infants developed HBV infection despite immuno-prophylaxis
(cases) and those whose babies remained uninfected (controls).
The
analysis included 12 transmission cases and 52 controls selected
from a provincial registry between 2000 and 2005. At the time
of prenatal screening, the mothers had a median age of 31
years and were a median 12 weeks into pregnancy. The researchers
looked at levels of HBsAg, HBeAg, and HBV DNA; HBV genotype
was determined for samples with detectable viral load.
Results
 |
Women
who transmitted HBV to their infants were significantly
more likely than control women to test positive for HBeAg
(77.8% vs 23.1%; P < 0.05). |
|
Among
the 51 mothers with detectable HBV DNA, cases had a significantly
higher median viral load than controls (5.6 x 10(8) IU/mL
vs 1750 IU/mL; P < 0.0001). |
|
Looking
at the 2 HBeAg negative case women who transmitted the
virus, 1 had undetectable viral load 8 months prior to
delivery and carried the sP120T mutation, while the other
had a viral load of 14 000 IU/mL. |
|
Overall,
a majority of HBV isolates were either genotype B (31.3%)
or C (31.3%), with no significant differences in genotype
distribution between the case and control women. |
Based on these findings, the study authors concluded, "In
this case-control study, transmission of HBV to infants was
more likely to occur in mothers positive for HBeAg and with
high HBV DNA."
These
results suggest that therapy to reduce HBV viral load before
or during pregnancy may further reduce the risk of mother-to-child
transmission.
Investigator
affiliations: Department of Medicine, University of Alberta,
Edmonton, Alberta, Canada; Centre for Communicable Diseases
and Infection Control, Public Health Agency of Canada, Ottawa,
Ontario, Canada; National Microbiology Laboratory, Winnipeg,
Manitoba, Canada; Provincial Laboratory for Public Health,
Edmonton, Alberta, Canada.
7/16/10
Reference
AE Singh, SS Plitt, C Osiowy , and others. Factors associated
with vaccine failure and vertical transmission of hepatitis
B among a cohort of Canadian mothers and infants. Journal
of Viral Hepatitis (Abstract).
June 11, 2010 (Epub ahead of print).
