Research on New Methods of Emergency Contraception. (ARTICLES).

The term "emergency contraception" refers to specific contraceptive methods that can be used as emergency measures to prevent pregnancy after unprotected intercourse. Emergency contraception is used after coitus but before pregnancy has become established; as such, it is considered a back-up method for occasional rather than regular use. (1)

All methods currently available for emergency use have limitations. That they can only be administered within a few days after intercourse restricts their usefulness and disqualifies for treatment women who cannot meet this deadline. Moreover, the methods, and the hormonal regimens in particular--such as high-dose estrogen or combined oral contraceptive tablets (known as the "Yuzpe" regimen)--may cause unpleasant side effects, including nausea, vomiting, headaches, dizziness and breast tenderness. These side effects can limit compliance and, in the case of vomiting, may affect the methods' efficacy.

Emergency methods are generally not as effective as other contraceptive methods. For example, even when the Yuzpe regimen is administered within the recommended 72 hours, it fails to prevent one-quarter of the pregnancies that would be expected without the therapy. (2) And although insertion of an IUD after unprotected intercourse is more effective and can be initiated later than the hormonal regimens (up until the expected start of implantation), its usefulness is limited because of the risk of infection, especially in victims of sexual assault or following intercourse with a new partner. IUD insertion is also not usually recommended for nulliparous women, and such women constitute a sizable proportion of those requesting emergency contraception. (3)

In addition to the drawbacks of these existing methods, their variety is very limited; a woman seeking emergency contraception has few choices at her disposal. Also, no currently available method is effective once implantation has commenced--unless endometrial aspiration is considered a method of emergency contraception. (4)

Emergency contraception could prevent many unwanted pregnancies. For example, a study carried out among 733 women requesting pregnancy termination in Oxford, United Kingdom, found that 410 women (56%) had had unprotected intercourse or experienced difficulty with the barrier method used. (5) Among these 410 women, 18 used emergency contraception without success; the remaining 392 did not use emergency contraception, mainly because they did not know it existed or where they could get it.

Had these 392 women used the Yuzpe regimen, about three-quarters of them would not have become pregnant. (6) Nevertheless, the fact that the Yuzpe regimen would not have prevented 25% of the conceptions among these women illustrates the very clear need for new and better methods of emergency contraception. In this article, we first explore what the ideal emergency contraception method would be. We then review those new methods that are now being tested and, finally, we conclude by outlining the prospects for improving emergency contraception in the future.

Ideal Emergency Contraception