First 'three person baby' born using new method
Sounds like mother & father's nuclear DNA, injected into the nucleus of a 3rd party's donor's egg cell, which contains its own mitochondrial DNA. Since mtDNA is normally inherited 100% from the mother (since the mother's egg cell supplies the mitochondria to the embryo), if the mother has a mitochondrial genetic disease, 100% of her children would normally inherit it.