Pill Less Effective for Overweight Women?
(Ivanhoe Newswire) -- A new study shows overweight and obese women who take oral contraceptives are more likely to get pregnant while on the pill.
Researchers from the Fred Hutchinson’s Public Health Sciences Division compared the weight and body mass indexes of 248 women who became pregnant while on the pill to that of 533 women who did not become pregnant while on the pill.
Results show overweight and obese women were between 60-percent and 70-percent more likely to get pregnant while on the birth control pill.
Women with a BMI of 27.3 or higher were 60-percent more likely to get pregnant while on the pill. A BMI of 27.3 is equivalent to a five-foot, four-inch woman who weighs 160 pounds or more. Women who were considered obese, with a BMI of 32.2 or higher, had a 70 percent greater risk.
Although researchers are uncertain why the correlation exists, they say metabolism may be to blame. Victoria Holt, Ph.D., lead author of the study, says, “The more a person weighs, the higher their basal metabolic rate, which can shorten the duration of a medication’s effectiveness.”
Holt also says heavier people have more liver enzymes that clear medications from the body. She says another possible explanation is hormones in the oral contraceptives are stored in body fat. “The more fat a person has, the more likely the drug is sequestered, or trapped, in the fat, instead of circulating in the bloodstream,” she says.
Holt suggests that overweight women who have completed childbearing should consider a permanent form of birth control such as sterilization, and overweight women who have not yet completed childbearing should use a backup form of birth control such as condoms while on the pill.
Holt says another recommendation would be to lose weight, even though the study did not examine the impact of weight loss on the pill’s effectiveness. She says, “I think losing weight, if one is substantially overweight, is a terrific idea for many health reasons and a laudable goal.”
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SOURCE: To be published in an upcoming issue of Obstetrics & Gynecology