The lis5 of essential oils (and therefore plants) that can definitely be said to have absolutely no abortifacient effect is very short. From memory, sweet orange/mandarin is about the only one definitely safe in the first trimester of pregnancy. Lavender and rosemary aren’t, although you’d probably have to use them in huge quantities for them to actually have an effect. But some of the ones like wintergreen, which features in Olbas Oil, have a much stronger link.