Complex therapy reduces vertical transmission risk

Once again research reveals that combination therapy most successfully reduces mother to child transmission in HIV-infected pregnant women.

A WITS (Women and Infants Transmission Study) – multicentre, prospective, natural history, ongoing since 1989 – published in the April issue of JAIDS examined data collected from 1,542 women who had singleton births between January 1990 and June 2000. Serial HIV RNA viral load measurements were taken from stored samples from the women and examined in relation to the HIV status of their babies.

For the 396 women receiving no antiretroviral treatment, the HIV transmission rate was 20%. For those using treatment the rates were: 10.4% for the 710 women receiving zidovudine (ZDV, AZT, Retrovir) monotherapy, 3.8% for 186 using dual therapy and 1.2% for those using HAART. Looking at transmission rates according to viral load found: 1% for <400; 5.3% for 400 to 3499; 9.3% for 3500 to 9999; 14.7% for 10,000 to 29,999 and 23.4% for 30,000 copies/ml. This showed a 2.4 fold increase in risk of transmission for every log10 increase in maternal viral load at delivery. Multivariate analysis adjusting for maternal viral load, duration of therapy and other co-factors, showed the odds ratio for transmission for women receiving dual therapy and HAART compared with those receiving ZDV monotherapy was 0.30 and 0.27 respectively.

Unsurprisingly both levels of HIV RNA at delivery and maternal antiretroviral therapy were independently associated with transmission. The protective effect of therapy increased with the complexity and duration of the regimen and treating women with HAART produced the lowest rates of transmission (and no doubt the healthiest mothers).

The investigators concluded that their data “suggests that use of such therapy, in addition to providing benefit to maternal health, may also result in further reductions in the risk of mother to child transmission.”