Actually, with the proper doses of hormones, at least at the start, you could probably get a baby to start growing in a male. The embryo is really highly driven to implant and start growing almost anywhere and protect itself against antibodies, etc., which is why even in women they can implant in bad places, like an ectopic pregnancy, which will eventually kill the woman and of course the baby. The whole uterus structure is there for the woman's benefit, to protect it from the baby, not because the baby won't grow anywhere else.