Im 15 weeks pregnant and i park there.go for it
Some of the places where I shop have "family" parking spots intended for a mom with a little one or little ones, so she won't have to walk very far. Others have spots designated specifically for pregnant women. I didn't park in those when my son was a toddler much as I would have liked to, but there really aren't very many of either kind so it seemed best to use them as they are designated. I used the ones for preggers ladies when I was pregnant, and the ones for mommies with little ones when that is what I was.
In short, go with how they are marked. If they are for pregnant ladies and you are pregnant, go for it.