Now pregnant women are allowed to take anti AIDS drug, nevirapine that prevents the transmission of H.I.V. from mother to child. In addition, they can have the medication without undergoing the antiretroviral treatment later in life. Since its an inexpensive drug, so may act as a boon for women in poor countries like Africa, Asia and Latin America. For three weeks, the preparation remains in the blood and if mother has the AIDS virus, its presence encourages the growth of nevirapine-resistant strains. That has given rise to fears that any antiretroviral drug cocktail containing nevirapine would be useless. However, the latest findings have postulated that such a cocktail is still of use if women simply delay it for six months after taking the protective dose of nevirapine. It has never been a faultless drug; when used for a long time, it might poison the liver and cause rashes, and the AIDS virus only needs to make a single mutation to develop resistance to it. In well off countries, women generally take two or three antiretroviral drugs to avoid passing the virus into their babies. But in poorer countries, women only seek medical help at the time of labor, leaving medical workers with little choice but single-dose nevirapine. A study done on nearly 4,000 women in Zambia have proved that most women getting triple therapy containing nevirapine do well even if they had single-dose nevirapine to protect their babies. It postulated that letting more time pass between the two events made a difference, and this study indicated that six months seemed to be the right amount of time.