Washington, Jul 22 (IANS): Hair and blood samples from three-month-old infants born to HIV-positive mothers surprisingly show exposure, both in the womb and from breast-feeding, to the antiretroviral drugs being taken by their mothers, says a study.

"We found high levels of exposure to three antiretroviral medications in the hair samples of 12-week-old infants who were uninfected by HIV," said study co-author, Monica Gandhi, associate professor of medicine at the University of California, San Francisco (UCSF).

"From looking at plasma level data at the same time point, we believe that transfer of two of the medicines from mother to baby occurs exclusively in the womb and transfer of the third medication occurs both in the womb and through breastfeeding," said Gandhi, according to a California statement.

The findings could lead to new ways to protect infants from HIV transmission and to better understand the development of toxicities and resistance to the drugs, researchers from UCSF and Makerere University, Uganda, said.

A single plasma level of a medication reflects drug exposure over approximately 24 hours.

Measuring the concentrations of antiretrovirals in a small hair sample reveals exposure over the past month.