A new report published by researchers with the Fred Hutchinson Cancer Research Center in Seattle says hormonal contraceptives, such as birth control pills and injectable progesterone, may increase a woman's chance of becoming infected with multiple strains of human immunodeficiency virus (HIV). The study examined over 100 women who contracted HIV while using a hormonal form of birth control.

The women increased their chances of contracting multiple strains of the virus by seven times. Researchers involved in the study speculate the high risk of developing multiple strains of HIV may be linked to the thinning of the vaginal walls, which is caused by a hormone in birth control pills.