Women with faulty mitochondrial DNA who want to have children can opt for IVF using eggs from a healthy donor. But two experimental techniques could allow affected women to have healthy babies that are genetically related to them. Both work alongside IVF.

The simpler of the two is called maternal spindle transfer (MST). First, doctors use standard IVF treatment to collect eggs from the mother. They then remove the nucleus from one of the mother’s eggs and transfer it into a healthy donor egg that has had its own nucleus removed. The reconstituted egg holds all of the mother’s healthy nuclear DNA, or 99.8% of her genes, plus the donor’s healthy mitochondria. This egg is then fertilised with the father’s sperm and the embryo is implanted into the woman like any other IVF embryo.

The second procedure is very similar. In pronuclear transfer (PNT), both mother and donor eggs are fertilised with the father’s sperm. Before the eggs have time to split into early-stage embryos, the chromosomes inside them are removed. Those from the donor egg are discarded, and replaced with the chromosomes from the mother’s egg. The resulting egg is fertilised and ready to grow into an embryo in the mother’s womb.

Treatments