Other Ongoing and Planned Studies

Studies of mechanisms of action

Although the treatment regimens used in emergency contraception may simply consist of altered doses of widely available contraceptive pills, women may hesitate to use them because of religious, cultural or other reasons. It is important, therefore, to clarify just how emergency contraceptives work so that women can decide if these methods are acceptable to them and can choose between the methods in case their modes of action are different. Depending on the stage of the cycle when the treatment is given, emergency contraceptives may affect follicular development, ovulation, and/or corpus luteum function and there is also evidence suggesting influence on the endometrium.

Since there was no information on the mode of action of the levonorgestrel regimen used in the above-mentioned multicentre trial (two tablets of 0.75 mg levonorgestrel with a 12-hour interval) a study was carried out to investigate the effects of this treatment on ovulation and on the endometrium, including several biological factors which are thought to be crucial to implantation. It is hoped that the results will give some indication of the mechanisms that are important for the effectiveness of levonorgestrel as an emergency contraceptive. On the basis of the interim results of this study, several new research initiatives have been planned.

Effectiveness, acceptability and side-effects of IUD insertion

The copper IUD can in certain cases be used as an alternative to hormonal methods of emergency contraception. A meta-analysis of 19 studies of postcoital insertion of IUDs revealed a failure rate of 0.1%, which suggests that this method may be 15 times more effective than the Yuzpe regimen. An IUD can be inserted up to the estimated time of implantation, which is around five days after ovulation (or five days after unprotected intercourse if the day of ovulation is difficult to estimate); thus, IUDs can be used 48 hours later than hormonal methods. The IUD is effective as soon as it is inserted, and therefore gives immediate protection for subsequent acts of intercourse in the same cycle. It also provides up to 10 years of subsequent contraceptive protection.

No studies have reported side-effects or morbidity after insertion of an IUD for emergency contraception. In standard practice, IUDs are usually inserted early in the cycle, which is not usually the case when they are used for emergency contraception. In terms of efficacy, all previous studies were retrospective and only one compared observed and expected numbers of pregnancies. In countries where the prevalence of IUD use is high, and where women who seek emergency contraception already have children, the IUD could be an excellent method of emergency contraception for many women. Therefore, it is important to look at the efficacy, acceptability, side-effects and possible complications of this method in a prospective study.

The Programme has launched such a study involving 18 centres in China in collaboration with the National Research Institute for Family Planning in Beijing. The study began in late 1997 and aims to recruit a total of 2000 women. The study protocol includes follow-up until one year after IUD insertion to observe the continuation rate and to assess late side-effects, if there are any. Final results from this study are expected to become available in the year 2000.

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