Me trying to figure out what a newborn centaur would look like. Most of the depictions of them show them laying down, helpless like human infants, but I think like horses, they'd be able to walk at birth. So the human would have to be able to support itself, so a newborn would have the physical development of a year old child. I also added a little more fat the horse part because a human child as skinny as a newborn foal would be horrifying.
This is probably the most sensible take on that question I've seen!