Pregnancy and childbirth scares the hell out of men because it is something women do that they cannot. And as it stands, the law favours female parents over men because of historic ideals of caring and nurturing. There are some men who hate women for that.
Also, for over a hundred years, childbirth has become the preserve of medical men, rather than women, obstetricians and reproductive science has taken over from community knowledge held by women. This has made birth safer, as technology has advanced. But it has also eroded the idea that childbirth was an exclusively female sphere.
So you can create an embryo in a lab, but it still requires a womb to grow. Natural biological women have wombs; so if you can harvest a womb, and put it in a man, you theoretically don’t need women to have children. So the one thing which women can do and men cannot, which is both a source of oppression and power, disappears.
I find it amazing that men can hate women so much that co-opting their biological functions, whilst erasing the means of discussing this and the need for women themselves, seems a reasonable thing to do. But they clearly do hate women. The question is why? That is what I don’t understand.