"We found high levels of exposure to three antiretroviral medications in the hair samples of HIV uninfected infants at twelve weeks of life," said study senior author, Monica Gandhi, MD, MPH, associate professor of medicine at the UCSF Division of HIV/AIDS at San Francisco General Hospital and Trauma Center (SFGH).
"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."
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, the researchers 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. The team therefore measured both plasma and hair levels of medications in babies whose mothers were taking HIV medications to get a better idea of when drugs are being passed from mother to baby. "Since fetuses start growing hair in the womb, hair sampling gives us an opportunity to examine exposures to drug before birth," said Gandhi.