1. monitor the vertical transmisssion rate following the introduction of interventions to reduce the risk of transmission, and changing maternal characteristics; 2. determine the contribution of maternal characteristics including virological markers and factors related to labour, delivery and birth, to vertical transmission; 3. describe the natural history of paediatric HIV infection at later ages and identify factors associated with rapid progression of disease and with long-term non-progression; 4. continue follow-up of uninfected children, including those who appear to have cleared infection; 5. coordinate and stimulate combined analyses of data from the principal perinatal transmission studies; 6. analyse results from the pilot phase of the randomised mode of delivery trial and explore and develop alternative vertical transmission intervention strategies; 7. clarify the progression of maternal HIV disease during pregnancy and after delivery and investigate patterns of care needs and provision in infected and uninfected children.
By December 1996, more than 2200 mother/child pairs had been enrolled from seven European countries. The rate of mother-to-child transmission in the ECS is currently 16.4% (95% confidence interval 14.5-18.3%). There has been a gradual increase in transmission rate over time as a larger number of mothers with HIV-related immunosuppression are being enrolled. Risk factors associated with increased transmission in the ECS include advanced maternal disease, prematurity and breastfeeding; findings which have had a major impact on policy. About 25% of infected children rapidly progress to AIDS in the first year of life, but by age 5 year an estimated 75% of infected children are alive. Currently about one-third of infected and uninfected children are aged over 5 years, but their number will increase substantially over the next 3 years. Although some questions have been answered, important questions still remain including the timing of vertical transmission (important for more effective targetting of interventions) and the long-term natural history and quality of life of vertically acquired HIV infection.