Background:  Zidovudine (ZDV) is the only antiretroviral licensed for use in pregnancy and has been the cornerstone for preventing mother-to-child transmission (MTCT) of HIV. With decreasing use of ZDV for treating HIV-infected adults in resource-rich settings, increasing numbers of pregnant women are exposed to HAART that does not contain ZDV (non-ZDV HAART) pre- or post-conception. We describe the risk of detectable maternal viral load at delivery, congenital abnormality, and MTCT in mother-child pairs with exposure to non-ZDV HAART and ZDV-containing HAART (ZDV HAART).

Methods:  An analysis of combined data from 2 European data sets from University College London Institute of Child Health:  the UK and Ireland National Study of HIV in Pregnancy and Childhood and the European Collaborative Study. All live singleton births from 2000 to 2009 with ≥14 days of documented HAART in pregnancy were included. Logistic regression was used to estimate adjusted odds ratios (AOR).

Results:  The study population comprised 7573 mother-child pairs of whom 1199 (15.8%) were exposed to non-ZDV HAART. Overall a third (2331 of 7557, 30.9%) of mothers were on HAART at conception. Exposure to non-ZDV HAART in pregnancy increased from 2000 to 2009 (P <0.01); 20.5% of women (141 of 688) on non-ZDV HAART had detectable delivery viral load compared with 30.0% (1058 of 3524) of women on ZDV HAART (AOR 0.60; 95%CI 0.72 to 1.11, P = 0.3) (data on delivery viral load missing for 3433 pregnancies). There was no evidence of an association between non-ZDV HAART and detectable delivery viral load in pregnancies with either pre- or post-conception HAART exposure. Risk of congenital abnormality was similar following non-ZDV HAART (2.7%, 31 of 1134) and ZDV HAART (2.7%, 166 of 6239; AOR 0.95; 95%CI 0.64 to 1.41, P = 0.8) with no significant difference between the treatment groups in a sub-analysis of pregnancies with first trimester HAART use (AOR 0.76; 95%CI 0.46 to 1.25, P = 0.3). The MTCT rate was 0.8% (7 of 903) following non-ZDV HAART compared with 0.9% (49 of 5227) following ZDV HAART (AOR 1.81; 95%CI 0.77 to 4.26, P = 0.2). Infant infection status was not yet reported for 20.0%, mainly for those born in 2008-2009.

Conclusions:  We found no evidence that exposure to non-ZDV HAART increases the risk of detectable maternal viral load at delivery, congenital abnormality, or MTCT. With increasing use of non-ZDV HAART, continued monitoring of pregnancy outcomes and longer-term consequences (on which we currently have sparse data) of in utero exposure is required.