The disclosure that 30 healthy babies were born after a series of experiments in the United States provoked another furious debate about ethics.
So far, two of the babies have been tested and have been found to contain genes from three 'parents'.
Fifteen of the children were born in the past three years as a result of one experimental programme at the Institute for Reproductive Medicine and Science of St Barnabas in New Jersey.
The babies were born to women who had problems conceiving. Extra genes from a female donor were inserted into their eggs before they were fertilised in an attempt to enable them to conceive.