Perinatal Transmission
Hepatitis B transmitted from mother to child is called "perinatal transmission" or "mother-to-child transmission (MTCT)" of hepatitis B virus. 1, 2
Understanding the Terminology
The medical literature consistently uses the term "perinatal transmission" to describe HBV infection that occurs from an infected mother to her infant. 1 This is distinguished from "horizontal transmission," which refers to infection acquired from household contacts or other sources after birth. 1
When Transmission Occurs
The majority of perinatal HBV transmission occurs during delivery, with rare instances of in utero transmission. 2 The virus is transmitted through exposure to maternal blood and body fluids during the birth process. 1
Risk Factors for Transmission
The risk of perinatal transmission varies dramatically based on maternal viral status:
For HBsAg-positive and HBeAg-positive mothers: Without prophylaxis, the risk of chronic HBV infection is 70-90% by age 6 months, or approximately 85% overall 1, 2
For HBsAg-positive but HBeAg-negative mothers: The risk drops to <10% without prophylaxis, or approximately 30% overall 1, 2
With proper postexposure prophylaxis (HepB vaccine and HBIG at birth): Only 0.7-1.1% of infants develop infection 2
Clinical Significance
Perinatal transmission is the primary driver of chronic HBV infection globally, particularly in endemic areas. 2 Infants infected perinatally have an 80-90% chance of developing chronic infection, compared to <1-12% when infected as adults. 2 This is why prevention of MTCT is a cornerstone of the WHO's goal to eliminate viral hepatitis as a public health threat by 2030. 3
Important Caveat
Breastfeeding by an HBsAg-positive mother does not increase the risk of HBV transmission to properly immunized infants. 1 This is an important reassurance for mothers who wish to breastfeed, provided the infant has received appropriate immunoprophylaxis at birth.