Antiretrovirals, mode of delivery and transmission risk

Polly Clayden, HIV i-Base

In an oral abstract presentation Dr David Shapiro presented data from the PACTG study looking at mother to child transmission rates among pregnant women with low viral loads. Data were collected from 3,081 women at 72 US centres between 1998 and 2002 and use of antiretrovirals, mode of delivery and viral load were evaluated in association with transmission risk.

In this study, 97% of women were in antenatal care, 61% of women already knew their status before their pregnancy and 88% began antiretrovirals in the first or second trimesters.

Dr Shapiro noted that between 1998 and 2002 there had been an increase in the use of combination therapy in pregnancy, and by 2002 the transmission rate was less than 1%. The rates for women receiving no antiretrovirals, monotherapy, dual therapy and three or more drugs were: 18.5, 5.1, 1.4 and 1.3 respectively.

At a viral load of less than 1,000 copies/mL and using multi therapy, the transmission rate overall was 0.6% and an elective caesarean section did not appear to offer any advantage.

Dr Shapiro concluded: “Transmission rate among women with plasma HIV RNA<1000 copies/mL did not differ significantly according to delivery route but was significantly lower with multi- versus single-agent ART.”

Responding to a question about transmission rate at less than 50 copies/mL, Dr Shapiro explained that at this viral load the rate was practically zero. “Is that data likely to be published?” the speaker asked, “We have been waiting for this for years.”


These findings shift emphasis on concerns about mode of delivery to careful maintenance of maternal health during pregnancy.


Shapiro D, Tuomala R, Pollack H et al. Mother-to-child HIV transmission risk according to antiretroviral therapy, mode of delivery, and viral load in 2,895 US women (PACTG 367). 11th CROI 2004. Abstract 99.

Links to other websites are current at date of posting but not maintained.