Impact of regimen and duration of therapy on risk of mother-to-child HIV transmission in Johannesburg
Polly Clayden, HIV i-Base
There are limited data describing the effects of HAART on mother-to-child transmission among HIV-positive women in Africa with CD4 counts <250 cells/mm3.
A poster authored by Risa Hoffman and coworkers showed an analysis of the impact of HAART regimen and duration of treatment on risk of transmission in women attending antenatal clinics in Johannesburg. 
This group had looked at transmission among women initiating HAART in pregnancy in an earlier analysis from this cohort. They found that for each additional week of HAART, the odds of transmission were reduced by 27%. We reported this study previously in HTB. 
In this more recent analysis they included both women who became pregnant while receiving HAART and those initiating HAART during pregnancy. The authors used chi square tests and logistic regression to evaluate the effects of regimen and duration on transmission. An infected infant was defined as having a positive DNA PCR at 6 weeks.
A group of 1115 women were followed from April 2004 until July 2008. At baseline the women were a mean age of 31 years and their mean CD4 count was 159 cells/mm3. Most women (97.3%) received a nucleoside backbone of d4T/3TC. Similar proportions received LPV/r (448; 40.2%) and EFV (469; 42.1%); and a smaller group of women received EFV (198; 17.8%).
Data for initiation of therapy were available for 874 women. Of these, 16.0% became pregnant while already receiving HAART. For those already on HAART the mean duration was 93.4 weeks. For those initiating HAART in pregnancy the mean duration was 10.7 weeks of therapy.
The investigators reported an overall transmission rate for women with known date of initiation of 4.7% (43/874). They found no significant differences between HAART regimens. This finding remained with or without adjustment for prior single-dose NVP.
Women who became pregnant on HAART had significantly lower transmission rates than women who initiated HAART during pregnancy, 0.7% vs 5.7%, p=0.01.
Women initiating HAART during pregnancy (n=553) had higher transmission rates with shorter duration of therapy: 9.3%, <4 weeks; 5.5%, 4-16 weeks and 3.5%, 17-32 weeks. There were no transmissions among women receiving >32 weeks of HAART. Each additional week of HAART reduced the odds of transmission by 8%, OR 0.92, p=0.02, CI 0.87-0.99.
To improve rates of MTCT, strategies are needed to facilitate earlier identification of HIV-infected pregnant women, they wrote.
Data continues to accumulate to support early identification of HIV-positive women in pregnancy and timely initiation of treatment.
- Hoffman R et al. Impact of antiretroviral therapy regimen and duration of therapy on risk of mother-to-child HIV transmission in Johannesburg, South Africa. 5th IAS Conference, Cape Town, South Africa.19-22 July 2009. Poster abstract WEPEB260.