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Contraception for obese women — Check options
Obesity is gaining ground in the United States. Are you prepared to offer women effective options? James Trussell, PhD, professor of economics and public affairs and director of the Office of Population Research at Princeton (NJ) University, reviewed current research at the 2007 Contraceptive Technology conferences to help clinicians select appropriate options.1
To discuss weight issues, clinicians need to understand the definitions for overweight and obesity. Both definitions are based on body mass index (BMI), which is determined by weight in kilograms divided by the square of height in meters. Among children and adolescents, overweight is defined as at or above the 95th percentile of the sex-specific BMI for age growth charts, while among adults, overweight is a BMI reading between 25 and 29.9. Obesity is defined as a BMI over 30, with extreme obesity is defined as a BMI over 40.2
A 2006 analysis of U.S. weight trends illustrates the problem facing clinicians today. Researchers report that in 2003-04, 17.1% of children and adolescents 2-19 years of age were overweight, and 32.2% of adults were obese, using estimates based on measured values of weight and height from the National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention's National Center for Health Statistics. Almost 5% of adults were extremely obese, the researchers found.2
In white, non-Hispanic women, 24% of women ages 20-39 were classified as obese, compared to 36% of Mexican-American, and 50% of black, non-Hispanic women, Trussell notes. In the 40-59 age brackets, those numbers increased to 38%, 48%, and 58%, respectively.2
Hormonal options OK?
Research in recent years has focused on the impact of weight in the efficacy of oral contraceptives (OCs), with some of the findings suggesting higher failure rates in pill users who are heavy.3,4
Trussell says his conclusion is that it is likely that very heavy or obese women have a higher risk of OC failure, particularly on the lowest-dose formulations, and may well be a threshold effect. However, the absolute risk still is likely to be modest: A 60% increase in risk implies an increase from 7% to 11% in the first year of typical use of OCs in the United States, Trussell points out.
While much attention has been focused on OC failure in obese women, clinicians should look at the risk of deep vein thrombosis (DVT) in this population, says Trussell. Obesity is a risk factor for venous thromboembolism, and OCs further increase the effect of obesity on DVTs, he states.
In reviewing clinical trial research of the contraceptive injection depot medroxyprogesterone acetate-subcutaneous (DMPA-SC) and the contraceptive implant Implanon (Organon; Roseland, NJ), researchers reported no pregnancies in women who used these methods, even those who were found to be obese, Trussell notes.5,6 In Implanon trials, women could be no heavier than 130% of ideal body weight, so we do not have much evidence about Implanon in obese women, Trussell notes.
Look at IUDs
Intrauterine contraception (IUDs) represents a "terrific" choice for obese women, says Trussell. Copper IUDs (ParaGard IUD, Duramed, a subsidiary of Barr Pharmaceuticals; Pomona, NY) are associated with a reduced risk for endometrial cancer.7 The levonorgestrel intrauterine system (Mirena IUS, Berlex Laboratories; Montville, NJ) reduces blood loss, reduces menorrhagia, and lessens dysfunctional uterine bleeding.8
Clinicians should weigh all factors when providing guidance on contraceptive methods for obese women, says Anita Nelson, MD, professor in the Obstetrics and Gynecology Department at the University of California in Los Angeles (UCLA) and medical director of the women's health care programs at Harbor-UCLA Medical Center in Torrance.
"I do very much appreciate the concerns for obese women and risk of thrombosis, but they also often have issues that could preclude use of other nonhormonal methods," says Nelson. "However, we cannot automatically assume that every obese woman over 35 is a candidate for or desires to use other effective contraceptives."
In helping women weigh their choices, Nelson advises that combined hormonal birth control methods provide many noncontraceptive benefits that are important to perimenopausal women. Therefore, the combination of age and obesity should only be considered at most a strong relative contraindication, not an absolute contraindication, she states.