This technology also known as three parent babies has been used for women who have hereditary mitochondrial disease, often of a neurological variety. These conditions are very rare. It may allow couples to have a healthy unaffected baby. While it was made legal in certain circumstances in the UK, there have been no pregnancies in the United Kingdom using this technique to date. There are a number of concerns about involving the ethics of experimentation on the human genome. For the time being use of this technique is very limited. It involves removing the nucleus from the donor egg and inserting the nucleus of the affected mother into the donor egg, avoiding passing on mitochondria from the affected mother. This means the resulting egg has the mitochondria of the donor but the nucleus of the patient with the disease. Importantly the mitochondria of the patient with the disease are not passed on. Further information about the safety of this technique needs to be required and the ethics concerned are considerable.