Hormonal contraception and STI acquisition explored.

Do hormonal contraceptive methods increase women's risk of acquiring sexually transmitted infections (STIs) other than HIV? This question is of critical concern, given that more than 100 million women worldwide use these methods. (1) Decreasing STI incidence by identifying and addressing any factors contributing to it is a major public health priority since untreated STIs in women cause important, long-term health consequences. Bacterial STIs--such as chlamydial and gonococcal infection--are associated with pelvic inflammatory disease, chronic pelvic pain, ectopic pregnancy, and infertility. Also, STIs in women may increase the risk of HIV acquisition (2) and transmission to sexual partners. (3)

Existing research on the relationship between hormonal contraceptive use and STIs is limited, and many studies suffer from serious methodological problems. (4) Further high-quality, prospective research is needed to reach informed conclusions about individual contraceptive methods and the risk of acquiring specific STIs. However, based on a review in 2005 of evidence on the topic, the World Health Organization concluded that its existing guidance was appropriate. That guidance places no restrictions on the use of combined oral contraceptives (COCs) or depotmedroxyprogesterone acetate (DMPA) by women at risk of acquiring an STI. (5)

A review of peer-reviewed articles describing research on contraception and STI risk published between January 1966 and December 2004 helps to clarify the matter. (6) The review, conducted by FHI and collaborating institutions,* focused largely on prospective studies that assessed contraceptive use prior to infection status. Cross-sectional studies were included but de-emphasized, since such studies cannot determine the sequence of contraceptive exposure and STI outcome, making it impossible to clearly establish the nature of any association. The review found:

* a…