There’s a lot of support for three-person in vitro fertilization: Mothers pass along mitochondrial DNA as well as nucleic DNA to their babies, while fathers only pass along nucleic DNA. Mitochondrial DNA doesn't carry information about character traits, but does carry certain diseases that can be life-threatening. Mothers can avoid passing along those diseases by using a donor's mitochondrial DNA instead, which is combined with the mother and father’s nucleic DNA to form a healthy embryo.