Transmission during labour and delivery (intrapartum transmission)

Scientists know that transmission occurs during delivery because:

  • One in two babies who turn out to be infected test HIV negative in the first few days of life.
  • Detecting HIV in babies increases rapidly during the first week of life.
  • Some newborn babies have an immune response similar when an adult first becomes infected.

It is also shown by the success in preventing transmission:

  • Treatment reduces transmission, even when only given in labour
  • From Caesarean section, before labour starts.

Transmission during labour and delivery happens when a baby passes through the birth canal. This period has the highest risk of contact with the mother’s blood and genital secretions.

HIV might also travel from the vagina or cervix to the foetal membranes and amniotic fluid, and through absorption in the digestive tract of the baby.

Or mixing of small amounts of mother and baby blood (maternal-foetal microtransfusion) might occur during contractions in labour.

The risk of transmission is increased in women not on ART if the baby takes a long time to be born after the membranes rupture (waters break).

Last updated: 1 December 2015.