None were born, but the researchers say this was due to obstetric complications rather than the fertility technique used, and that it would work in future.

However, the approach is now reported to have been banned in China, where the pregnancy was created. It was already banned in the US and UK, and the news of the attempt has led to renewed criticism of fertility research by anti-abortion groups.

Some children have already been born with three genetic parents, but the new research has prompted additional controversy because the method used shares a technical step, called nuclear transfer, with cloning procedures. However, the US scientist who developed in animals the technique used by the Chinese researchers says: "It's nothing to do with human cloning."...