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Background:  Rates of mother-to-child HIV transmission (MTCT) have declined substantially with the use of ART. However, of the multitude of regimens used during pregnancy and the neonatal period, only a few have been formally evaluated in clinical trials. Their efficacy thus has to be assessed using observational data.

Methods:  In the European Collaborative Study, HIV-infected pregnant women and their infants are followed prospectively in 10 European countries. Data on 2589 infants enrolled between 1994 and September 2004 who received some form of neonatal antiretroviral prophylaxis  to prevent MTCT were analyzed from this ongoing study.

Results:  Half of the pregnant women on HAART had initiated therapy before pregnancy. Most (53%) infants received zidovudine (ZDV) monotherapy (n = 1360), 215 (8%) ZDV and single dose (sd) nevirapine (NVP), 2 didanosine (ddI) + sd NVP, 806 (31%) sd NVP and 206 (8%) a combination of ≥ 2 drugs excluding sd NVP. All but 8 of the infants receiving sd NVP alone were from Ukraine. Most neonates receiving ZDV monotherapy received this orally for a median of 6 weeks (range 2 to 12 weeks), but in one center ZDV was given intravenously for 2 weeks (194 neonates). The most common of the 10 combination prophylaxis regimens used were ZDV+ lamivudine (3TC) (n = 149) and ZDV+3TC+sd NVP (n = 27) (both for a median duration of 4 weeks, range 2 to 7 weeks). Infants receiving combination prophylaxis were more likely to be the second or more child enrolled in the study compared with those receiving ZDV monotherapy (20% vs 12%, c² = 8.81, p = 0.003). The MTCT rate in 2001 to 2003 was 0.99% (95% CI 0.32 to 2.30%) overall; 8 of the 206 infants with combination ART neonatally were infected (3.88%, 95% CI 1.24 to 6.52%), which reflects the late initiation of antenatal ART in some of their mothers. Of the 1424 neonates, 39 (2.74%, 95% CI 1.89 to 3.60%) with mono ZDV were infected. The association between MTCT risk and duration and intensity of antenatal and neonatal ART will be assessed in multivariate analyses.

Conclusions:  There is considerable variation in the prescribing of antenatal and neonatal prophylaxis, both over time and between centers. This highlights the lack of an evidence-base on which to guide clinical practice.

Keywords: MTCT; ART regimen; Europe