I'm pretty sure it's fine, just don't go whiffing the bottle of it much, eating more than a mint candy or cup of herbal tea, or using it topically on yourself. Generally though mint is pretty mild and common. I did find that it deters mice where you put it but if you really want the mice gone from your home you have to trap them until there are no more.
I am a doterra consultant and it is safe to use our peppermint, actually all our oils while pregnant. I have used it topically on my belly when i get tummy aches the last 2 pregnancys. I have never had a problem. Now i cannot and will NOT speak for any other company or any health food store oils. They only have to be 15% pure oil to be considered PURE...so do your research if you are to use any essential oil...pregnant or not. You dont want a bunch of chemicals being absorbed by your bloodstream :)
happy to answer any other questions if need be...
oh and alot of people stay away from peppermint while nursing because it can be used to dry up milk, but i never had a problem, but then again i wasnt rubbing on my chest :)
I second lisathena on doTERRA, but that is the ONLY peppermint oil I know for sure is safe. Many EO companies don't ever recommend putting their oils on topically. I certainly can't say I'd want to be smelling them at any time, much less in early pregnancy... but then, that's why I use the oils I use :)
The answer mostly depends on how pure the oil is.