Hi Olive
I teach nails & beauty.
Yes its fine to soak your acrylic nails off with acetone when pregnant. A few times throughout your pregnancy is fine, you don't want to be using acetone every week!
Just make sure if you are putting the acetone in a bowl (not plastic) and then putting your hands in, that you put a towel over your hands so that you don't breath in too much acetone, it does evaporate very quickly.
I hope this helps xx