Mode of delivery

Mother-to-child transmission (MTCT) of HIV can occur at any stage of pregnancy, during labour and delivery, or after delivery through breastfeeding. HIV transmission is most likely to happen when mothers are not on antiretroviral treatment and have higher viral loads over 1000 copies/ml.

The US Perinatal HIV Guidelines Working Group recommendation is that women on HAART with a viral load under 1000 copies/ml should be counselled that the risk of transmission is low, caesarean delivery has an uncertain benefit, and that it carries more risk than vaginal delivery. For women with viral load over 1000 copies/ml  or unknown viral load, a scheduled cesarean delivery at 38 weeks is recommended; however, women should be counselled concerning the risks to cesarean delivery to mother and infant.¹

Caesarean delivery should not be routinely offered to women whose viral load is less than 1000 copies/ml. It was formerly thought that caesarean section was one of the most effective ways to limit transmission, but with routine antiretroviral use in pregnancy, that is no longer the case. Earlier studies done by the European Collaborative Study and the US Women and Infants Transmission Study demonstrated a benefit to caesarean delivery, but in those studies, few of the women were on HAART and the analysis was not adjusted for viral load level.^{2 3} 

More recent data show the benefit of HAART in reducing viral load and subsequently, perinatal transmission. The MTCT rate in PACTG 312 was 1.5% in women on ARV during pregnancy, even though some of the women were only on monotherapy.⁴

PACTG 367 found a similar transmission rate of 1.3% in women on multi-agent therapy. That study showed that among women with less than 1000 copies/ml, transmission rates were 0.8% in women who had elective caesarean delivery and 0.5% in women with all other delivery modes. For those women who were taking AZT monotherapy, transmission rates were 4.3% after elective caesarean and 1.8% with all other modes.⁵

Data from the later European Collaborative Study showed a transmission rate of 1.2% in the subset of women who were on HAART. This study did show a benefit to elective caesarean section, but when results were adjusted for use of any ARV therapy, a significant difference between transmission rates according to mode of delivery was not found.⁶ 

The risks involved with caesarean delivery include postpartum infection and fever. A study done by the European HIV in Obstetrics Group looked at HIV-negative and HIV-positive women who delivered vaginally or by elective caesarean section. Overall, HIV-infected women experienced more complications regardless of mode of delivery; however, minor complications occurred in nearly 13% of the women who had a vaginal delivery as contrasted to nearly 43% of those who chose an elective a caesarean delivery.⁷  

The guidelines conclude that scheduled caesarean delivery for PMTCT carries a greater risk than vaginal delivery. If an elective caesarean delivery is performed, ACOG (American College of Obstetricians and Gynecologists) recommends performing it at 38 weeks to avoid the risk of membrane rupture or labour starting, but doing so at this time does carry a slight increase in risk of infant respiratory distress that would require mechanical ventilation.