This method is far more popular among African women than birth control pills. HIV risk also appeared to increase in women who took contraceptives in pill form. But the researchers did not study enough of them to say for sure.

The study involved close to four thousand heterosexual couples in Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda and Zambia. Either the man or the woman already had HIV when the study began. The researchers tested the partners over a two-year period.

The study appeared last week in the journal Lancet Infectious Diseases.

Africa has the largest number of people living with HIV. South of the Sahara, the virus has spread mainly through sex between men and women.

Experts point out that even if the popular contraceptives increase the risk of HIV, there are also risks to increased pregnancies. Sub-Saharan Africa has high rates of pregnancy- and childbirth-related deaths in women and health problems in babies.

The global development organization FHI 360 notes that earlier studies of this issue produced mixed results. It says a higher quality study is urgently needed to compare users of injectable hormones and other contraception methods. Such a study, it says, would take at least four to five years to produce results.

And that's the VOA Special English Health Report. I'm Faith Lapidus.