The “abortion pill” RU-486 could become a new form of daily contraceptive. The pill usually contains oestrogen and progesterone, but oestrogen increases the risk of breast cancer. Progesterone-only pills often cause irregular bleeding and spotting.

RU-486 contains mifepristone, a synthetic steroid that stops ovulation through a different mechanism. David Baird and colleagues at the University of Edinburgh, UK, gave 72 women a low daily dose of mifepristone or the progesterone-only pill for 24 weeks. Both pills were equally good at preventing pregnancy, but mifepristone caused significantly less unwanted bleeding (Human Reproduction, DOI: 10.1093/humrep/dem177).