A rapid test to detect HIV in women during labor could help doctors prevent mothers passing the virus to their babies, scientists said on Sunday.

About 700,000 infants worldwide are infected with HIV each year, either in the womb or through breastfeeding. Many pregnant women in poor countries do not know if they are infected with HIV and unwittingly transmit the virus to their newborns.

But doctors in the United States said the speedy test can show whether a woman has HIV or not in about 66 minutes, allowing doctors to give a drug to the mother before the birth and to the child shortly afterwards to prevent virus transmission.

“Rapid testing during labor can enable pregnant women with undocumented HIV status to learn their HIV infection status so they can receive antiretrovirals,” Dr Mardge Cohen, director of Women’s HIV Research at Cook County Hospital in Chicago, told an international AIDS meeting.

The rapid test costs $8 to $12, he said.

Cohen and scientists from the U.S. Centers for Disease Control and Prevention (CDC), who reported their findings in the Journal of the American Medical Association (JAMA), studied the impact of voluntary testing among women in labor at 16 U.S. hospitals in six cities.

The CDC estimates between 280 and 370 infants are born with HIV each year in the United States despite U.S. recommendations for universal prenatal HIV screening and the widespread use of antiretroviral drugs in HIV-positive pregnant women.

The numbers are much higher in the developing world, where drugs and testing are not widely available. Medical studies have shown drugs can reduce mother-to-child transmission from about 25-30 percent to 10-13 percent.

The 4,849 women who took part in the study were counseled and tested in hospital.

Thirty-four tested positive for the virus and were given antiretrovirals almost immediately. Their babies were given a drug shortly after birth. Only three were born with HIV.

“Implementing rapid testing in labor and delivery is feasible,” Cohen said.

In a separate study presented at the 15th International AIDS Conference opening in Bangkok on Sunday, Dr Taha Taha, of the Johns Hopkins School of Medicine in Baltimore, Maryland said a study in Malawi showed the drug nevirapine alone was as effective in reducing the risk of HIV transmission at birth as combining it with zidovudine, also known as AZT.

GlaxoSmithKline’s AZT is the oldest HIV drug. Nevirapine is made by German drug company Boehringer Ingelheim.

The risk of transmission was the same in both groups. But Taha said if women developed a resistance to nevirapine, a second drug could be helpful.

“If development of resistance is minimized by adding zidovudine, then it could have a greater utility,” he added.