Fantasy creature question! Do centaur babies reside in the human stomach or animal stomach? Also, how many months until a baby centaur is born?
Given that these are mammals and baby mammals need to pass through the vagina to enter the world, the uterus is likely to reside in the abdomen closest to that birth canal.
I would presume that’s the equine abdomen, given the relative size of the creature and that’s where there’s most room to fit a developing foetus, and the shortest distance for giving birth.
Otherwise if you put the uterus in the human abdomen, then you either need the whole, mature foetus to move the entire length of the equine body, which is insane, or you need to relocate the human genitals to in between the front legs, which is awkward for everything, including copulation.
I would expect centaur gestation to take between 9 and 11 months