Use of an oral contraceptive (OC) did not decrease overall sexual function in a rare randomized controlled trial on the issue, published online August 15 in the Journal of Clinical Endocrinology & Metabolism.

However, the levonorgestrel-containing oral contraceptive (OC) used in the study did slightly decrease three of seven measures in the validated Profile of Female Sexual Function (PFSF) tool, those of desire, arousal, and pleasure. And that may make a difference to some women choosing birth control, the authors write.

The authors, led by Niklas Zethraeus, PhD, of the department of learning, informatics, management, and ethics at Karolinska Institutet, aren’t suggesting providers change prescribing practice, according to Dr Hirschberg. But she added that the possible side effects should be recognized.

The combination used for this trial was 150 g of levonorgestrel and 30 g of ethinylestradiol (Neovletta, Bayer Schering Pharma), which is the most widely prescribed oral contraceptive in Sweden, the authors write. Dr Hirschberg said oral contraceptives containing levonorgestrel are recommended as the first choice in many countries since this combination has been associated with the lowest risk of venous thrombosis.

The group randomly assigned 340 healthy women ages 18 to 35 years to placebo and 332 to the combination OC. Participants took one capsule every day for 21 days, but not during the fourth week, for 3 months.

Baseline data was collected in days 1 through 7 before the start of treatment and final data collection was at the end of the third treatment cycle. At both points, a blood sample was taken for analyses of hormones and binding proteins. Participants completed three surveys: the weekly Sexual Activity Log (SAL), the PFSF, and the personal distress scale (PDS)

The average PDS scores and frequency of satisfying sexual episodes in 1 week were also similar between the groups: For PDS the mean difference was 3.63 (P = .083); for satisfying episodes, the mean difference was -0.57 (P =.054).

First Study of Its Kind

The authors write that most previous studies in this area have been retrospective and not randomized or controlled. Only two small placebo-controlled randomized studies were published between 1978 and 2011, and both had inconclusive results.

Colleen Krajewski, MD, MPH, an obstetrician/gynecologist with Magee-Womens Hospital of University of Pittsburgh Medical Center, Pennsylvania, said oral contraceptives are “among the most misunderstood medications.”

She told Medscape Medical News that the current study illustrates that, while some individual women report their sexual function is affected by their contraceptive, “when we look at a large group of women, on average, we don’t see a big difference in objective measures of sexual function compared with placebo.”

She said she commonly hears patients say their libido has decreased and then ask for their birth control to be adjusted. This study will help give them confidence that for most women, the cause is likely not the brand of birth control they are using, she said. The study also highlights an understudied topic. “We should absolutely address issues of sexuality and libido,” she said, “and address them in a multifactorial way.”

Different types of combined OCs have different risk profiles and side effects. Therefore, the findings can’t be generalized for all OCs, the authors acknowledge. Some pills are associated with mood changes, acne, increased appetite, and weight gain, depending on the progestin component and type of regimen.

“Further placebo-controlled studies are needed to evaluate effects on sexual function by alternative OC combinations,” Dr Hirschberg said.

If data from other OCs show fewer or no adverse effects on sexual function, that could influence medical decisions. Sexual dissatisfaction is a key reason women stop taking OCs, risking unwanted pregnancies, the authors note.