Mother to child transmission of human immunodeficiency virus type 1 (HIV) is the most common aetiology of paediatric HIV infection throughout the world. Research has yielded important information regarding the timing and mechanisms of, as well as interventions to interrupt, mother to child transmission of HIV.

The biological plausibility of a lower risk of transmission with caesarean section prompted investigations of mode of delivery as a risk factor for mother to child transmission of HIV. The cumulative evidence from epidemiological studies performed over the past two decades, culminating in the publication of an individual patient data meta-analysis of prospective cohort studies from North America and Europe¹ and a randomised clinical trial from Europe,² demonstrates a lower risk of mother to child transmission of HIV with caesarean section before labour and ruptured membranes (hereafter referred to as scheduled caesarean section, or SCS). The individual patient data meta-analysis¹ compared the risk of mother to child transmission among approximately 8000 HIV infected women who underwent SCS with that of women with any other mode of delivery. The risk of transmission was 50% lower among women who delivered by SCS in analyses allowing for adjustment for other factors (adjusted odds ratio (OR) = 0.43 (95% confidence interval (95% CI): 0.33, 0.56)). Further analyses revealed an 87% lower likelihood of transmission among women who underwent SCS and who received antiretroviral therapy during the antepartum, intrapartum, and postnatal periods (likely zidovudine prophylaxis) compared with those with other modes of delivery and no antiretroviral therapy (adjusted OR = 0.13 (95% CI 0.09, 0.19)). In the randomised clinical trial of mode of delivery,² SCS resulted in a lower risk of transmission than vaginal delivery in analyses of both allocated (OR = 0.2 (95% CI 0.1, 0.6)) as well as actual modes of delivery (OR …