(Slough) if you think you might need emergency contraception.
A woman can get pregnant if a man's sperm reaches one of her eggs (ova).
It is also not side-effect free, with up to one in eight of the women taking part in trials dropping out due to dizziness, fatigue and sleep problems.
It is not known yet how much it will cost, but is unlikely to be widely prescribed by a health service struggling to find cash to fund treatment of life-threatening illnesses.
It was created as an anti-depressant but those taking part in trials said it did nothing to boost their mood but did wonders for their sex drive.