A new study shows that HIV-positive women are twice as likely to transmit the virus to a sexual partner if they use hormone-based birth control, The New York Times reports.

Similarly, researchers from the University of Washington found that HIV-negative women raised their chances of getting the virus if they were on the pill or taking a hormone shot like Depo-Provera.

As reported at the 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention in Rome, the results indicate a need for follow-up studies, and researchers cautioned women to not immediately change their birth control practices.

The study was conducted from 2004 to 2010 in Kenya, Uganda, Rwanda, Botswana, Zambia, Tanzania and South Africa. Nearly 2,500 HIV-positive women with HIV-negative partners participated in the study. One third of the women took hormonal contraception. The partners of those women had a 2.61 percent chance of getting HIV within one year.

Within the same region and time period, researchers looked at 1,300 couples in which the men were HIV positive and their female partners were not. In this group, 20 percent of the women were on a hormone-based birth control, mostly injections, and they had a 6.6 percent chance of seroconverting within a year’s time.

To read the Times article, click here.