Short AZT course can protect fetuses.

Treatment with AZT (zidovudine) during the last few weeks of pregnancy cuts mother-to-fetus transmission of HIV by half, a study in Thailand shows. Based on these results, U.S. and United Nations researchers have stopped giving pregnant women an inactive drug, or placebo, in worldwide studies of HIV transmission, a research protocol that some critics had called unethical. All of the women are now receiving AZT.

Tests have shown that roughly one child in five born to HIV-positive women who are not receiving medication becomes infected with the virus before or during birth. In a study of 397 women in Thailand, a 3- to 4-week course of AZT cut HIV transmission from 18.6 percent to 9.2 percent. The women began getting the drug in the 36th week of pregnancy and continued until childbirth, the federal Centers for Disease Control and Prevention (CDC) in Atlanta reports.

The Thai women were taking AZT orally, and their infants received no medication after birth. The regimen costs about $80 per pregnancy, much less than the longer, slightly more effective $800 treatment typically prescribed in the United States and other industrialized countries. The more expensive course, which starts in the 26th week of pregnancy, cuts transmission rates to about 7 percent, says Jack Killen, a physician at the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Md.

U.S. agencies are funding studies on mother-to-infant HIV transmission in 10 African countries and the Dominican Republic. A study in Uganda will include some women who receive another antiviral drug along with AZT during late pregnancy, Killen said.

The Thai study prohibited breast-feeding because HIV might be transmitted that way. In forthcoming studies, researchers plan to study the risks of breast milk, a key source of nutrition for infants in developing countries, Killen says.