Background Most HIV-positive women on combination antiretroviral therapy (cART) with undetectable HIV viral load now deliver vaginally. Studies from the pre-cART era showed an association between duration of rupture of membranes (ROM) and mother-to-child transmission (MTCT). Here, we investigate the impact of ROM duration on MTCT rates in the cART era.

Methods The National Study of HIV in Pregnancy and Childhood collects data on all pregnancies in HIV-positive women in the UK and Ireland. We analysed singleton deliveries 2007–2012 in women receiving cART in pregnancy, excluding in utero transmissions.

Results ROM duration and infant’s HIV status was available for 1973 pregnancies. The MTCT rate was 0.3% (6/1973), with no evidence of an association with ROM (≥4 vs <4 hours) overall, among term deliveries (≥37 weeks), or term deliveries with viral load <1000 copies/ml (Table). There was only one transmission in 237 preterm deliveries; this was also the only transmission among the 97 deliveries where ROM was ≥24 h.

Conclusions This is the largest study to date to examine the effect of ROM on MTCT. The MTCT rate following ROM was low (0.3%), with no evidence of an association with duration of ROM.