[Clinical study of emergency contraception with low-dose mifepristone]

Abstract

Objective: To evaluate the effectiveness of 10mg mifepristone used for emergency contraception in a large population in China. A total of 4945 women was recruited in 31 clinical centers in 18 provinces and municipalities in China in a descriptive clinical trial with one dose treatment.

Method: A single dose of 10 mg of mifepristone was given to women who has one episode of unprotected intercourse within 120 hours.

Results: There were 28 cases lost to follow-up. An analysis of 4917 cases showed a pregnancy rate of 1.4% (95% CI 1.1, 1.8) and an effectiveness of prevention of pregnancy 82.2% (95% CI 77.5, 86.2). No trend of increase of pregnancies with delay of treatment was found. Increase of risk of pregnancy in women who had unprotected intercourse after treatment is about 11.1 times higher. Other factors, such as age, body mass index, menstrual phases when unprotected intercourse occur and previous live birth also affect the risk of pregnancy. Side effects were mild and in small proportion of women, such as nausea and vomiting in 9.2% and other side effects in 0.7% approximately 3.7% of women. Delay of menstruation over 7 days occurred in 6.5% of women.

Conclusions: The expanded study further confirmed the high efficacy of 10 mg mifepristone for emergency contraception. It is also safe and acceptable.