Mode of delivery

Caesarean section delivery has been associated with a reduction in transmission in a number of studies, although not in all^{119,181,207,223,296}. In some centres, Caesarean section has become a common mode of delivery for HIV positive women, despite the lack of conclusive evidence at the time. In 1995 in the United Kingdom, 44% of HIV positive mothers were delivered by Caesarean section²⁶².

A 1994 meta-analysis of prospective follow-up studies showed a small reduction in transmission with Caesarean section²²⁴. A more recent meta-analysis included five European and ten North American prospective studies totalling over 8500 mother-infant pairs. Elective Caesarean section reduced the risk of mother-to-child transmission by more than 50%, after adjusting for antiretroviral therapy, birth weight and maternal infection stage²⁹⁷.

A French study showed a transmission rate of 0.8% in women who had received long-course antiretroviral treatment and had an elective Caesarean section, compared to 6.6% with vaginal delivery²²⁸. A study in Switzerland reported no transmission in 45 women who received long-course ZDV and an elective Caesarean section²²⁷.

A randomized controlled trial of mode of delivery has been undertaken in Europe²²⁶. This trial randomized in excess of 400 women to elective Caesarean section delivery or expectation of vaginal delivery. Three out of 170 infants (1.8%) born to women in the Caesarean section group were HIV infected compared with 21 out of 200 (10.5%) born to women in the vaginal delivery group. A treatment effect odds ratio of 0.2 (95% confidence intervals 0.1-0.6).

Two thirds of the women taking part in this trial were exposed to zidovudine during pregnancy. In this sub-group 0.8% of babies born to the women allocated to Caesarean section were HIV infected compared with 4.3% of those born to women allocated vaginal delivery. This gives an odds ratio of 0.2 with 95% confidence intervals of 0-1.7. For women not exposed to zidovudine during pregnancy the odds ratio for transmission was also 0.2 suggesting that the protective effect of Caesarean section persists whether women were or were not prescribed zidovudine during pregnancy.

In addition there were no serious adverse complications in either group. Postpartum fever was reported more commonly in women delivered by Caesarean section although the overall incidence was low.

The use of Caesarean section must take into account the possibility of maternal morbidity and mortality^109,110,298, the availability of safe operating facilities, the potential increased service commitments and the accessibility of maternity services for women in future pregnancies.