An international ban on reproductive cloning is urgently needed, say embryologists and organisations working in the field, after a claim last week that a fertilised egg produced by reproductive cloning had been implanted into a woman's uterus.

Panos Zavos, professor emeritus of reproductive physiology-andrology at the University of Kentucky, in the United States, claimed at a press conference held in London last week that he had implanted a cloned embryo into a woman's womb. He said that the embryo had been produced from the immature egg of an infertile 35 year old woman …