Hormonal Contraceptives May Not Work Well in Overweight Women

Oral hormonal contraceptives such as the birth control pill are a popular form of birth control because of their convenience and reliability. But women who are overweight or obese may want to consider using an alternative form of birth control. A new study shows that hormonal contraceptives, including birth control pills, patches, and vaginal rings, may be less effective in obese and overweight women.

Oral Contraceptives Pills and Obesity

After reviewing eleven different research trials involving almost 40,000 women, the authors of a study published in the Cochrane Database concluded that oral hormonal contraceptives and patches and vaginal rings are less effective in women with higher body weights and BMIs. On a positive note, the rate of pregnancy doesnt seem to be higher in obese women who use an implant or an injectable form of contraception.

Why Are Hormonal Contraceptives Less Effective in Overweight and Obese Women?

Hormonal contraceptives could be less effective in overweight and obese women for a variety of reasons. The hormones in oral contraceptives, patches, and rings are stored in fat tissue. If the contraceptive hormones are sequestered away in fat, there are less of them available to prevent pregnancy. Plus, most hormonal forms of contraception contain very low levels of hormones for safety reasons " and the levels may not be high enough for women of a certain weight or BMI.

Obese and overweight women may also metabolize oral hormonal contraceptives faster, which could reduce the amount of hormones available in the bloodstream to prevent pregnancy. Giving higher doses of hormones isnt necessarily a good solution, since this could increase the risk of serious side effects such as blood clots, stroke, or heart attack in some women.

Should Obese and Overweight Women Use Hormonal Contraceptives?

Until more is known, obese and overweight women should considering using an implantable or injectable form of birth control, as opposed to pills, patches, or vaginal rings. These forms of hormonal therapy were effective in the study irrespective of body weight or BMI. Another option is to use a barrier method instead. Discuss the options carefully with your doctor.

References:

http://www.ncbi.nlm.nih.gov/pubmed/20614470?dopt=Abstract