With an estimated 1,800 babies born with HIV every day in the most resource-starved nations, there has long been an urgent need for an inexpensive preventive for mother-to-child viral transmission. Finally, a glimmer of hope: In July, U.S. and Ugandan researchers reported results of a study in that East African country that found that giving one pill of the nonnucleoside nevirapine (Viramune) to the mother during labor and one liquid dose to the baby after delivery cut the transmission rate to only 13 percent. By contrast, giving AZT to mothers every three hours during labor and to newborns twice a day for a week resulted in a 25 percent transmission rate. And the nevirapine approach is 70 times cheaper than the short-term AZT, costing only $4 per dose. (The U.S. standard remains oral AZT for the mother starting in the second trimester, then intravenous AZT during labor and delivery, followed by six weeks of the oral or intravenous drug for the infant, which studies have found can cut transmission rates to less than 10 percent. Total cost: $800.) Researchers estimate that widespread use of the nevirapine one-two punch in developing countries could prevent HIV transmission to up to 400,000 babies yearly.