

According to a quick search (memory is foggy) it is set around 2350 — humans have colonized most of the solar system. They have fusion reactors and ships capable of traveling from Earth to the Jovian moons (I think? I’m not sure if they go further). There is definitely advanced medicine regarding surviving spaceflight (i.e. performing maneuvers that put you in otherwise unliveable circumstances without drugs).
The circumstances of Earth, Mars and the Belt are delicate. Without spoiling too much, no the Belters do not have good health care.
I like the Expanse, I was a fan of the books before the show. The show is good, some aspects are better than the books — but I haven’t actually finished the show itself. Give it a shot if you’re into hard science fiction!
Edit: I should note, a baby born in the belt could be taken to Mars or Earth and they would grow up fine. The Belters themselves aren’t riddled with genetic diseases or anything like that, growing up in low g’s is just fucked.
Well, in the books the physical differences between Earthers, Martians and Belters are very striking. Due to the lower gravity on Mars, and the even lower gravity on spinning asteroids in the belt; Earthers end up being much shorter than their counterparts with Belters looking very bizarre. I would imagine it would result in them being shorter, and if the gravity is high enough it could completely stunt the baby’s growth in a sort of inverse to what the Belters go through.