CHAPEL HILL -- Pregnant women infected with HIV may have two weapons for reducing the risk of transmitting the AIDS virus to their baby: taking a combination of AIDS drugs and opting to give birth by cesarean section, according to new research at the University of North Carolina at Chapel Hill. Early findings from a study of infants in North Carolina born to HIV-infected mothers from January 1, 1998 to September 30 1999 show increases in the use of combination anti-retroviral drug therapy during pregnancy and elective C-sections. These increases were accompanied by further reductions in HIV transmission during childbirth compared to that of the previous four years - from an average of 12 per year for 1994-1996 to about 4-6 per year for 1997-1999.
The findings will be presented for the first time Wednesday February 2, 2000 at the 7th Conference on Retroviruses and Opportunistic Infections in San Francisco.
"These are preliminary results," said Susan A. Fiscus, Ph.D., study leader and associate professor of microbiology and immunology at UNC-CH School of Medicine. She notes that since 1998 only one of the infants born via elective c-section has been infected, but 58 of the 74 (78%) also received combination anti-retroviral therapy (ART).
"It's unclear whether the beneficial effect is due to combination anti-retroviral therapy or whether there's an additional effect of elective c-section if the woman is already getting adequate anti-retroviral treatment, especially if it's combination treatment."
Apart from finding out if combination ART was on the rise in the North Carolina study population, Fiscus and her study collaborators also wanted to know what drugs HIV-infected pregnant women were taking. "Maternal combination ART increased from 2% in 1996 to 68% in 1999," she said. "Mothers used 15 different combination regimens in 1998 and 10 in 1999."
Combination ART involving AZT, 3TC, and nelfinavir, was the most common last year. But despite the sparse clinical evidence of safety and efficacy of that combination in pregnant women, Fiscus says her findings appear supportive of its use.
"Our data would suggest that it does seem to be effective in preventing perinatal transmission, and so far we've seen no untoward effects in the babies or mothers."
In the new study, eight of eleven infected infants in 1998-1999 received either no ART, short course treatment with AZT only, or had mothers who did not adhere to the ART regimen. These findings point to the importance of reducing blood concentrations of HIV, or viral load.
"It's been shown in several studies that the higher the viral load the more chance you have of transmitting the virus to the baby," Fiscus said. "And what would work best for lowering the viral load in the blood for the mother is probably going to be best for the baby. And it most cases that's going to be combination anti-retroviral therapy."
As to the importance of mode of childbirth as a risk factor for HIV transmission, the UNC researcher said the Europeans "are way ahead on this and have been suggesting that c-sections might be useful in preventing some of the transmission from mother to baby."
While the research evidence favoring elective c-section for HIV-infected mothers is sparse, physicians -- including North Carolina doctors who treat Medicare populations -- appear to be spreading the word. From 16% of the population Fiscus surveyed in the first six months of 1998, elective c-sections increased to 47% in 1999. (In general, about 10% of all births are by elective c-section.)
"What I think is interesting is that even in the absence of any clear data that says elective c-sections are important in addition to combination anti-retroviral therapy, many of the women here in North Carolina are getting them," said Fiscus.
"Women should be aware of all of the data, including the additional risks associated with surgery, and make an informed decision in consultation with their physician."
Note to media: Dr. Fiscus can be reached at 919-966-6872. Jan 30 thru Feb 2, contact Dr. Fiscus at the Marriott Hotel, San Francisco, 415-896-1600, Retrovirus Conference message center. UNC School of Medicine contact: Karen Stinneford, 919-966-6047, email:kstinnef@unch.unc.edu Leslie Lang, 919-843-9687; email: llang@med.unc.edu