Abstract and Introduction
Emergency contraception, or postcoital contraception, is a modality of preventing pregnancy after unprotected sexual intercourse or to avert potential contraceptive failure. The controversy revolves around the definitions of pregnancy and induced abortion. If one utilizes the medical definition accepted by the WHO, pregnancy only begins with implantation; therefore, there can be no abortion without a pregnancy and emergency contraception can in no way be equated to an abortion. The problem is that – ethically at least – there is a contention that a new human life begins right after the fertilization process is completed through full syngamy. Thus, using these parameters, it becomes vital to ascertain exactly the mechanism of action of postcoital methods. Emergency contraception exists in two different forms: the hormonal and the intrauterine. Hormonal emergency contraception was first proposed by Yuspe in the form of 100 µg ethynyl oestradiol plus 500 µg levonorgestrel taken twice at a 12-h interval. At the end of the 1900s, a second regimen – consisting of 1500 µg of levonorgestrel, within 12 h – was introduced and found in clinical trials to be more effective than the Yuspe regimen, if taken as early as possible after an unprotected intercourse. This method therefore completely replaced the Yuspe regimen in common use. Over the last 20 years, the WHO has developed a third regimen based on the use of the selective progesterone receptor modulator mifepristone; different dosages have been tested: >50, 50–25 and <10 mg, taken as a single dose, and they have been found to be equally effective, although the incidence of a delayed onset of the subsequent cycle increases with higher dosages. Two clinical studies have now compared the levonorgestrel and the mifepristone regimens; the first, conducted by WHO, compared three options: levonorgestrel, given either twice at the dose of 750 µg, or as a single 1.5-mg dose, and mifepristone, at a single dose of 10 mg. The second compared levonorgestrel (750 µg, twice) with mifepristone (10 mg, single dose). Both studies concluded that all regimens possess similar effectiveness. Recently, a new formulation consisting of a new selective progesterone receptor modulator, ulipristal acetate, has been licensed in several European countries and in the USA. At the single dose of 30 mg it shown to be a more potent inhibitor of ovulation than levonogestrel and can be effectively taken until 120 h after unprotected intercourse.
The WHO defines 'emergency contraception' (EC) as those contraceptive methods that provide a woman with a safe means of preventing an unwanted pregnancy, following unprotected sexual intercourse or in the event of potential contraceptive failure.
Other terms, such as 'postcoital contraception' or 'the morning-after pill' can cause confusion and therefore should no longer be used. In fact, the various methods available today can be used up until a maximum of 5 days after unprotected intercourse; thus, the term morning-after pill is both inappropriate and misleading because, on the one hand it implies the need to acquire the treatment within 12 h and, on the other, it describes the method as exclusively involving the use of a pill, whereas not all methods utilise the oral route of administration.
By definition, contraception comprises all methods capable of preventing pregnancy. In the past, methods acting after fertilization but before implantation were named 'interceptive', although this expression was never widely used. Today, EC includes all methods that act before the beginning of pregnancy; any definition of the beginning of pregnancy is given. In contrast to this, any method active after the establishment of a pregnancy (implantation) must be defined as abortifacient.
It has been argued that – in reality – a new human life exists at syngamy, once fertilization has taken place. Therefore, for those taking the ethical position that pregnancy begins at fertilization, in theory at least, EC should be listed among abortifacient methods. Even in this case, however, the levonorgestrel-based method seems to act only before fertilization and, therefore, should be listed as 'contraceptive'. In addition, it has been argued that – for ethical as well as practical reasons – it is certainly less problematic to act as quickly as possible after fertilization and that – irrespective of the definition of pregnancy – EC should be preferred to induced abortion. In this connection, it has been estimated that approximately 75% of unwanted pregnancies could be avoided if women were educated and properly used EC.
There are two medically accepted methods for EC utilized today worldwide: hormonal methods (combined estrogen–progestin pills, progestin-only pills and methods based on the administration of a selective progesterone receptor modulator mifepristone (SPRM) and intrauterine methods, that is, the postcoital insertion of a copper-bearing intrauterine device, which will not be discussed in this paper.
Expert Rev of Obstet Gynecol. 2011;6(5):569-576. © 2011 Expert Reviews Ltd.
Cite this: Emergency Contraception - Medscape - Sep 01, 2011.