Oral Contraceptive Suppression of Ovarian Function in Obese Patients

Abstract & Commentary

By Frank W. Ling, MD, Clinical Professor, Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine, Nashville, is Associate Editor for OB/GYN Clinical Alert.

Synopsis: Ovarian suppression with oral contraceptives is similar for normal-weight and obese patients.

Source: Westhoff CL, et al. Ovarian suppression in normal-weight and obese women during oral contraceptive use: A randomized controlled trial. Obstet Gynecol 2010;116:275-283.

In this double-blind protocol, normal-weight (body mass index [BMI] 19.0-24.9 kg/m2) and obese (BMI 30.0-39.9 kg/m2) women with regular periods and normal ovarian ultrasound took one of two types of oral contraceptives (OCPs): either 21-day monophasic pills with 20 mcg ethinyl estradiol/100 mcg levonorgestrel or 30 mcg ethinyl estradiol/150 mcg levonorgestrel. Compliance was assessed with serial serum levels of levonorgestrel. One hundred eighty-one subjects of 226 completed the study. Among patients who were consistent users of the pills, suppression of follicular development was similar for both doses of pills. Ovulation rates were similar among consistent users of either normal or obese weights.

Commentary

Admit it. You've already answered the questions asked by this study many times with various patients. I know I have. The fact is, though, good data from good Level I evidence has been lacking and we've all responded to our patients with the best information available to us. Now we can tell our patients with confidence that OCP failures in obese patients are not due to a lack of efficacy of the pills in obese women, but, instead, a result of non-compliance. There is always that potential lingering concern for an obese woman starting on OCPs that the pill won't be strong enough, but that issue can now be addressed directly. Both doses of pills were similarly effective.

The authors were extremely diligent in designing a study that we clinicians could look to with confidence. By drawing twice weekly bloodwork and performing regular ultrasounds, better conclusions were drawn about compliance with pills and follicular development. We can be even more confident in the results because, as expected, there was more spotting in the 20 mcg pill compared with the 30 mcg pill.

What we can tell our patients is very real, i.e., the inconsistent users of the pills had substantial rates of ovulation (38.5%) whether they were obese or not. Consistent OCP users experienced ovulation only 2.7% per cycle. By enrolling only ovulatory patients, the authors were able to minimize the potential impact of anovulation among the general population of obese patients. Of interest, obese patients were less compliant in taking their OCPs. Because the authors were able to document who was compliant or not (by looking at ovarian ultrasound and progestin levels as a marker of ovulation), this aspect of the study was also useful to all of us: Patients sometimes report that they are compliant when they actually are not. (Surprise, surprise! Patients don't always report events to us accurately?!)

I really liked the study from its simplicity standpoint and also its real-life application. As often as we give out OCPs, being able to predict outcomes and warn patients of limitations of their use is critical. Of particular interest is the recent declaration from the federal government that all forms of contraception are to be covered by all insurance plans. This will bring many more patients into the contraceptive arena, some of whom are new or less-informed. We would each be wise to make sure that we ascertain the level of each patient's understanding of the contraceptive of choice in this new era. It doesn't help much to have contraception covered by insurance if the contraception isn't being used correctly. n

(Editor's note: Compliance is critical for all users of hormonal contraception. The interactions of obesity and OCP efficacy are complex and will be analyzed in an upcoming Special Feature by Dr. Edelman.)