Introduction At the end of 2008, 1 in 486 pregnant women in the UK were infected with HIV. Prior to widespread use of Highly Active Anti-Retroviral Therapy (HAART), Caesarean section was recommended to decrease vertical transmission. Current guidelines (British HIV Association and Royal College of Obstetricians and Gynaecologists) suggest that women with an undetectable viral load (VL) may undergo vaginal delivery. Pre-HAART data indicate that prolonged labour and prolonged rupture of membranes (>4 h) should be avoided as this increases the risk of transmission, but the risks post-HAART are unknown.

Aim/Methods A retrospective case note review was undertaken on 63 pregnant women (66 pregnancies) with known HIV attending St Mary's Hospital between 2006 and 2009.

Results In 52 pregnancies (79%) VL was undetectable by delivery, after a median of 9.5 weeks HAART treatment. Full obstetric information was available in 47 cases. All women with a detectable VL underwent Caesarean section. Vaginal delivery was achieved in 29 (62%). Four patients were induced and underwent artificial rupture of membranes. Membrane rupture to delivery interval was greater than 4 h in seven women (24%). Average labour length was 4 h 52 min. All babies were HIV negative 3 months postnatally.

Discussion A high percentage of women are able to achieve undetectable VLs using current HAART regimens, allowing the possibility of vaginal delivery. There were no episodes of vertical transmission, despite seven women having prolonged ruptured membranes. More work is needed to investigate the risk of vertical transmission in women with undetectable VLs who wish to undergo vaginal delivery.