WHEN a couple first have sex, they are quite likely not to have planned to do so, and may not have used any sort of contraception. Condoms split or come off; women forget to take oral contraceptives. For all sorts of reasons a couple may wake up one morning wondering whether the woman might have become pregnant as a result of sex the previous night. But the outcome does not have to be left to chance.
Treatment with a 'morning-after pill' first came into use in the late 1960s, when it was shown that if large doses of oestrogen were given within 92 hours of unprotected sexual intercourse, pregnancy was usually prevented. The treatment was given for several days and almost invariably made the woman feel sick and vomit. A few years later the Yuzpe method was introduced; this was treatment with a combination of two hormones, an oestrogen and a progestogen. Two doses were given 12 hours apart. Around half the women treated felt sick and a quarter vomited, but the success rate was estimated to be close to 99 per cent.
A newer hormone treatment is now being given in Britain, using the hormone antagonist mifepristone (RU 486), first developed as a medical treatment to induce abortion. Two research studies recently published (one from Edinburgh in the New England Journal of Medicine and one from Manchester in the British Medical Journal) have compared mifepristone with the old Yuzpe method. In both studies the treatment with mifepristone was 100 per cent successful, whereas the Yuzpe method had a few failures - four out of 398 women in Edinburgh and five out of 191 in Manchester. Both drugs caused some side-effects, but fewer women felt sick or vomited while taking mifepristone. Women given the Yuzpe treatment usually knew it had worked because they had some menstrual bleeding within a few days. But in those given mifepristone, the next menstrual period was sometimes delayed, and three became pregnant a couple of weeks after their treatment, having mistakenly believed that it had failed.
Even using mifepristone, postcoital contraception is a clumsy technique with substantial drawbacks, and it should not be used repeatedly. The risks to health of repeated use of high doses of oestrogen are well known - the hormone may cause blood clotting in the veins and arteries - and furthermore the Yuzpe method is not always effective. No one really knows the effects of repeated use of mifepristone, but current thinking is against it. Another possible treatment that is sometimes used is the insertion into the uterus of an intrauterine contraceptive device; this is virtually 100 per cent effective as emergency contraception and also provides continuing protection, but it is not usually recommended for young women who have not had children.
The final reason for discouraging women from psychological reliance on postcoital contraception is that there is no equivalent postcoital method of preventing infection with sexually transmitted virus diseases such as HIV infection (though a woman who has been raped can be protected against some sexually transmitted bacterial diseases by treatment with antibiotics). Safe sex is safe in terms both of contraception and infection.
The morning-after pill needs to be taken within 72 hours (three days) of intercourse and not 92. The new hormone treatment mifepristone (RU486) is licensed in this country as an alternative method of abortion; it is still only at trial stage as an emergency contraceptive.