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22-08-2010 | Gynaecology | Article

Contraceptive pill just as effective in obese as in normal-weight women


Journal Abstract

MedWire News: Obese women are not at higher risk for pregnancy during consistent oral contraceptive (OC) use than their normal-weight counterparts, study findings show.

Previous research results have indicated that OC failure varies by body weight or body mass index (BMI).

However, such studies have reported on unintended pregnancy rates among normal-weight versus obese OC users, which does not explain whether the pregnancies were a result of OC failure or due to behavioral differences in OC use.

Carolyn Westhoff (Columbia University Medical Center, New York, USA) and colleagues compared ovarian suppression via transvaginal ultrasonography in 96 normal-weight (BMI 19.0-24.9 kg/2), and 54 obese (BMI 30.0-39.9 kg/m2) women taking OCs for at least 3 months.

Hormonal assays (measuring levonorgestrel levels) undertaken on days 2 to 21 of the study cycle determined whether the women were consistent, inconsistent, or non-OC users.

Overall, 21 participants ovulated during the study. However, just four (2.7 percent) of these women were consistent OC users; three of normal weight, and one obese woman.

"Our findings strengthen the message to patients that the pill will only work if it is taken every day," said Westhoff.

"Weight does not seem to have an impact on suppression of ovulation, but consistency of pill-taking does," she concluded.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Sarah Guy