Vertical transmission rates for HIV in the British Isles: estimates based on surveillance data

Objective To estimate and interpret time trends in vertical transmission ra tes for HIV using data from national obstetric and paediatric surveillance registers. Design Prospective study of HIV infected women reported through obstetric s urveillance. HIV infection status of the child and onset of AIDS were repor ted through paediatric surveillance. Rates of Vertical transmission and pro gression to AIDS rate were estimated by methods that take account of incomp lete follow up of children with indeterminate infection status and delay in AIDS reporting. Setting British Isles. Subjects Pregnant women infected with HIV whose infection was diagnosed bef ore delivery, and their babies. Main outcome measures Mother to child transmission of infection and progres sion to AIDS in children. Results By January 1999, 800 children born to diagnosed HN infected women w ho had not breast fed had been reported. Vertical transmission rates rose t o 19.6% (95% confidence interval 8.0% to 32.5%) in 1993 before falling to 2 .2% (0% to 7.8%) in 1998, Between 1995 and 1998 use of antiretroviral treat ment increased significantly each year, reaching 97% of live births in 1998 . The rate of elective caesarean section remained constant, at around 40%, up to 1997 but increased to 62% in 1998, Caesarean section and antiretrovir al treatment together were estimated to reduce risk of transmission from 31 .6% (13.6% to 52.2%) to 4.2% (0.8% to 8.5%). The proportion of infected chi ldren developing AIDS in the first 6 months fell from 17.7% (6.8% to 30.8%) before 1994 to 7.2% (0% to 15.7%) after, coinciding with increased use of prophylaxis against Pneumocystis carinii pneumonia. Conclusions In the British Isles both HIV related morbidity and vertical tr ansmission are being reduced through increased use of interventions.