Essential oils?

I apologize in advance if this is a stupid question, but I've been reading a lot of conflicting things about essential oils online. I bought a diffuser and a few different oils, including a Rosemary. After I bought it, I looked and saw that Rosemary shouldn't be used during pregnancy because it can potentially trigger contractions. When they say "don't use" do they mean directly on the skin? Or will it be okay to use it in a diffuser for my house? Again, sorry if this is a dumb question, I'm genuinely confused!