When does HIV transmission occur from mother to baby?
Although mother to child transmission (MTCT) of HIV can take place during pregnancy, the highest risk of transmission is during labour and delivery. Depending on breastfeeding practices and the duration of breastfeeding, there is also a substantial risk of MTCT of HIV during breastfeeding.
Without intervention, it is estimated that 40 out of every 100 babies (40%) born to HIV-infected mothers will be HIV-infected. Table 16.1 shows the risk of transmission during pregnancy, during labour and delivery, and during breastfeeding. Sixty percent of babies of HIV-infected mothers will not acquire the virus at all. However, it is not possible to predict which HIV-infected mother will transmit the virus to her child, so you must provide PMTCT services to all HIV-positive pregnant women.
Table 16.1 Estimated percentage of mother-to-child transmission (MTCT) of HIV from an HIV-positive mother to her baby during different transmission periods.
| Transmission period | Maximum risk of HIV MTCT without any intervention |
|---|---|
| During pregnancy (in the uterus) | 5–10% |
| During labour and delivery | 10–15% |
| During breastfeeding after birth | 5–10% |
| Overall risk without breastfeeding | 15–25% |
| Overall risk with breastfeeding to 6 months | 20–35% |
| Overall risk with breastfeeding to 18-24 months | 30–45% |
| Total risk of MTCT | 20–40% |
Looking at the data in Table 16.1, how does the period of breastfeeding affect the risk of MTCT of HIV?
The longer the breastfeeding period, the greater the risk of MTCT of HIV. If a baby is breastfed to 6 months the risk of MTCT is 20-35%. The risk rises to 30-45% if breastfeeding goes on till the baby is 18-24 months old. This is a 10% rise in the risk of MTCT.
If HIV infection can be detected and treated effectively in the antenatal period, then it will reduce the chances of MTCT during labour and delivery or breastfeeding. Next, we look at the factors that increase the risk of MTCT during pregnancy.