What is the mode of maternal transmission of HIV to her infant? Does HIV cross the placental barrier or does transmission occur during the trauma of the birth process? If it occurs from birth trauma, would C-section be of benefit in reducing transmission?

Hi. Thank you for your question.

An infected mother can transmit the virus to her baby one of three ways. First is during pregnancy itself, since the virus can pass through the placenta, and go directly into the fetus. Second, transmission could occur during delivery, since the baby is being directly exposed to the blood of the mother. Third, the virus can be transmitted from mother-to-child during breastfeeding.

Without any type of medical intervention, the chances of the virus being transmitted from mother to child is about 25%. With medical intervention, we can reduce that risk to about 8%. This intervention includes giving the mother AZT and other drugs during pregnancy, and treating the newborn baby with AZT and other drugs, immediately after the baby is born.

Because a Cesarean section (C-section) also exposes the baby to a lot of blood, there has been no documented benefit of doing a C-section, rather than a vaginal delivery. The only means we have seen so far that reduces mother-to-child transmission is by drug therapy, as discussed above. It is because of this effective drug therapy that we now strongly recommend HIV testing for all pregnant women.

If you have any further questions, please feel free to contact the Centers for Disease Control at 1.800.232.4636 (Nationwide).