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Comment and Controversy

Are OCs less effective in obese women?

March 2008 · Vol. 20, No. 03

“Contraception for medically complex patients,” by Daniela A. Carusi, MD, MSc

Thanks to Dr. Carusi for tackling a timely and important topic. The subject of oral contraceptive (OC) efficacy in obese women becomes more significant as our collective body mass index rises. However, a recent cohort study utilizing survival analysis and sampling weights to adjust for response rates found no association between obesity and OC failure after controlling for age, race/ethnicity, and parity.1 We found similar results in a secondary analysis of 4,496 women in the combined Asthma in Pregnancy and Health in Nutrition and Development Study.2 Only a well-powered, prospective cohort will prove or disprove the association with certainty.

Susan Richman, MD
New Haven, Conn

Dr. Carusi responds: Many nuances influence choice of contraceptive

Dr. Richman is correct: We lack an appropriate study confirming diminished OC efficacy in obese women. Until such a trial is conducted, I think it is important to point out that some people misinterpret “less effective” as “ineffective” and fail to prescribe adequate contraception for obese women. However, as with most patients, pregnancy poses more risk to obese women than does combined hormonal contraception. If that is the only effective method that an obese woman can accept and comply with, it may be the best method for her. On the other hand, because of its high efficacy and lack of demonstrated cardiovascular or thrombosis risk, intrauterine contraception should be strongly considered for this group of patients.

Dr. Jelsema also raises an important point. However, when a patient has a history of sickle cell disease and mild stroke, the WHO treats DMPA differently than other progestin-only methods, including pills and Implanon; the latter are WHO category 2 (benefits generally outweigh risks), while DMPA is category 3 (risks generally outweigh benefits). To explain this distinction, the WHO points to the hypoestrogenic effect and reduced high-density lipoprotein cholesterol level in women who are taking DMPA.

Although there is a single small study (25 subjects) showing that DMPA may reduce painful crises in sickle cell patients, it is not sufficiently powered to confirm cardiovascular safety, particularly in a patient who has already suffered a cerebrovascular accident.1 For the patient described in my article, who was able to demonstrate excellent compliance with pill-taking and was willing to use barriers for prevention of sexually transmitted infection and backup contraception, progestin-only pills were thought to be her safest option.


1. Brunner Huber LR, Toth JL. Obesity and oral contraceptive failure: findings from the 2002 National Survey of Family Growth. Am J Epidemiol. 2007;166:1306-1311

2. Richman S, Belanger K. Is there an association between BMI and OCP failure? Contraception. 2008 [in press].

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