A new morning after pill that works up to five days after unprotected sex has been developed by scientists.
The drug is potentially more effective than current pills available to women over the counter, which have a time limit of 72 hours.
Studies show that EllaOne prevents up to two-thirds of unwanted pregnancies if used within the first three days after intercourse.
Even if it is taken five days after, its success rate is still 50 per cent. The regular pill prevents 60 per cent of pregnancies if taken as instructed.
EllaOne was launched in Britain in October last year and is only available on prescription. Levonorgestrel, which has been available on the NHS since 1999, can be obtained over the counter in pharmacies.
Professor Anna Glasier from NHS Lothian in Edinburgh said that for this reason, it will be some time before EllaOne becomes the main method of emergency contraception.
"Many women find it quicker and more convenient to go to the pharmacy than visit a GP," she told the Daily Mail.
Pills are not the only emergency contraception available to women. The copper intrauterine device can be fitted into the womb by a doctor or nurse within five days of unprotected sex and is almost 100 per cent effective, according to the NHS.