Background: HAART dramatically reduces mother-to-child transmission of HIV allowing vaginal delivery if the viral load is low. This study provides data for the optimum timing of short-term HAART in pregnancy.
Methods: Retrospective multicentre cohort study of pregnant women commencing HAART in London and Brighton, UK. Demographics, gestation, drug class, CD4 cell count, and viral load results were collated. Survival curves for reaching a viral load less than 50 copies/ml were stratified by initial HIV viral load. Cox's proportional hazards regression model was adjusted for demographics and immunovirological parameters.
Results: Viral load was less than 50 copies/ml in 292 of 378 pregnancies (77.2%) by delivery. Pretreatment viral load was associated with the time taken, and the proportion achieving a viral load less than 50 copies/ml at (P≤0.001). When baseline viral load was less than 10 ,000 copies/ml, gestational age at HAART initiation did not affect success up to 26.3 weeks gestation. When viral load was more than 10 ,000 copies/ml, deferring HAART past 20.4 weeks reduced the probability of reaching less than 50 copies/ml by delivery (P=0.011). When baseline viral load was more than 100, 000 copies/ml the likelihood of reaching a viral load of less than 50 copies/ml was low (37%: hazard ratio 0.31), and dependent on the length of time on HAART. The hazard ratio for a nonnucleoside reverse transcriptase inhibitor regimen achieving a viral load less than 50 copies/ml compared with a protease inhibitor was 0.7 (95% confidence interval 0.52-0.94).
Conclusion: With a viral load more than 10, 000 copies/ml and especially with a viral load more than 100 ,000 copies/ml, the probability of achieving either less than 50 copies/ml by the time of delivery is compromised by delaying initiation of short-term highly active antiretroviral therapy beyond 20.4 weeks gestation. Current UK and other guidelines for when to commence START may therefore limit the chance of vaginal delivery.