When a sperm and an egg join together they form a zygote. This is what a baby originates as. A zygote is only one cell. A single cell grows/duplicates to multiple cells by the process of mitosis....
A baby has two sets of chromosomes: one from the mother and one from the father.
As such, even a baby who's egg comes from the mother growing it in her womb, the DNA will only be a 50% match.
If...