Review Determines Most Effective Emergency Contraception Method

A new review has found that the hormonal pill mifepristone is the most effective emergency contraception method to prevent unwanted pregnancy. In the United States, however, the drug has not gained government approval for this use.

With emergency contraception, women use hormonal pills or a copper intrauterine device to prevent pregnancy after unprotected intercourse. These methods are used after sex but before pregnancy occurs.

Most recommend use of the hormonal methods within 72 hours of unprotected sex. A clinician can insert a copper IUD up to five days after the estimated time of ovulation.

The aim of the systematic review was to determine which of several available emergency contraception methods is most effective in preventing pregnancy after unprotected sex.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

“Unwanted pregnancy is a common problem,” writes lead reviewer Linan Cheng, M.D. “Worldwide, about 50 million pregnancies are terminated each year.”

Cheng added that despite the number of terminated pregnancies, “except for a few Western European countries and China, emergency contraception is largely under-utilized worldwide.”

Cheng is director of the Shanghai Institute of Family Planning Technical Instruction in China.

She and her colleagues evaluated 81 clinical trials, 70 of which occurred in China. The review comprised 45,842 women who sought emergency contraception after one act of unprotected intercourse.

The clinical trials compared the effectiveness of the hormonal pills mifepristone and levonorgestrel, the Yuzpe regimen (a method of combination use of estrogen and progestogen repeated once 12 hours apart) and the copper IUD.

Most of the clinical trials studied mifepristone in two different doses — low dose (less than 25 milligrams) and middle dose (25 to 50 milligrams) and compared levonorgestrel in either a single dose of 1.5 milligrams or two (split) doses of 0.75 milligrams given 12 hours apart.

The Cochrane reviewers found mifepristone, given in the middle dose, was “superior to other hormonal regimens” in preventing pregnancy.

More pregnancies occurred with levonorgestrel than with either mid-dose mifepristone or low-dose mifepristone. Single-dose levonorgestrel had the same effectiveness as the split dose. Levonorgestrel, however, was more effective than the Yuzpe regimen in preventing pregnancy.

The Cochrane reviewers concluded that mifepristone “should be the first choice of hormonal emergency contraception” where available. If it is not available, “single-dose levonorgestrel 1.5 mg should be offered.”