MPs will hold a crucial vote later to decide whether to allow the creation of babies using DNA from three people.
They will have a free vote on the technique, which is aimed at preventing deadly genetic diseases being passed from mother to child.
The UK could become the first country to introduce laws to allow the creation of babies from three people.
It has sparked fierce ethical debate and senior Church figures have called for the procedure to be blocked.
However, if there is a “yes” vote in the Commons, then the first three-person baby could be born as soon as next year. It could eventually help about 150 couples a year.
The technique, which was developed in Newcastle, should help women like Sharon Bernardi, from Sunderland, who lost all seven of her children to mitochondrial disease.
Mitochondria are the tiny compartments inside nearly every cell of the body that convert food into useable energy. They have their own DNA which does not affect characteristics such as appearance.
Defective mitochondria, which are passed down only from the mother, lead to brain damage, muscle wasting, heart failure and blindness.
The technique uses a modified version of IVF to combine the DNA of the two parents with the healthy mitochondria of a donor woman.
It results in babies with 0.1% of their DNA from the second woman and is a permanent change that would be passed down through the generations.