If you haven't seen this animation of what is happening inside our bodies as baby grows, you must. Very sciencey, very cool, and it explains a lot. Just move the dial to go through the months:
https://www.msichicago.org/whats-here/exhibits/you/the-exhibit/your-beginning/make-room-for-baby/interactive/Peeing every 5 seconds is explained. Watch that bladder!
Re: This explains A LOT (body animation)
Eta: autocorrect fail!