The aim of this form of IVF is to stamp out serious diseases which can be passed from a mother to her children. Around one in 200 babies are born each year in the UK with a defect in the way cells are supplied with energy.
One in 6,500 babies can suffer potentially life-threatening diseases including a form of muscular dystrophy and conditions leading to hearing and vision loss, heart, lung and liver problems, and bowel disorders. An estimated 12,000 people in the UK live with the diseases.
More top news
Hollywood actor Mickey Rourke made a return to the boxing ring today aged 62, defeating an opponent less than half his age.
Poland has warned the UK that it will block any plans to discriminate between British and EU citizens.
The world's biggest ritual animal slaughter has begun in Nepal, amid protests. Readers may find images in this article distressing.