Babies born with three 'parents'

Scientists in the US have announced that babies have been born carrying the DNA of three parents: two women and a man. The babies were the result of a controversial program using ooplasmic transplantation - effectively adding cytoplasm from a donor woman's egg to that surrounding the nucleus of an infertile woman's egg.

The technique was designed to increase success levels of IVF treatment in older women by introducing mitochondria - the powerhouses of cells - from the cytoplasm of the eggs of younger women. The actual genetic information of the mother will not be changed, but because mitochondrial DNA (mtDNA) carries its own genetic information, it has been reported that, technically, the babies have three parents.

The introduction of mtDNA has also caused concern because the 'mixture of genes' will be inheritable - the genetic information contained in the mitochondria will be passed down the maternal line to future generations.

The cytoplasmic transplantation technique is banned in many countries because of concerns about genetic implications and ethical and moral concerns, and the Human Fertilisation and Embryology Authority has decided not to license it in this country. But it has been claimed by a team led by Dr Jacques Cohen, from the Institute for Reproductive Medicine and Science of St Barnabas in New Jersey, that in recent years about 30 children worldwide have been born using the technique. Fifteen of the babies have been born following treatment at the Institute.

The technique has been criticised by an editorial in Science, which warned that it is naive to assume that mtDNA does not affect the wider workings of the human body. The HFEA called it an unwelcome development that 'adds additional concern to their existing worries'.