The successful fertilisation of an egg using biological material from two women may have moved the world closer to three-parent babies. Researchers at St Mother Hospital in Kitakyushu, Japan, have experimented with repairing the damaged eggs of older women by using eggs from younger donors. The usefulness of this process is disputed. Some doctors say it could improve chances of fertilisation and prevent genetic defects; others worry that the DNA of three people might lead to genetic problems.

Older women often display abnormalities in the cytoplasm of their eggs and this can lead to IVF failure. But the Japanese team believes that injection of a nucleus into the cytoplasm of a donor (usually a younger woman) could sidestep this problem. They conducted an experimental run of this process, and it was found to be successful for 25 out of 31 eggs. Seven formed "early stage embryos" when sperm was injected.

In 2001, a furore erupted when an IVF centre in New Jersey injected cytoplasm from young eggs into older women's eggs to improve their quality. Fifteen babies were born using the technique. The doctors claimed at the time that it represented "the first case of human germline genetic modification resulting in normal healthy children." In the wake of the ensuring furore, the US Food and Drug Administration banned the technique. ~ London Telegraph, Nov 12;