I think it’s important for a couple to maintain their sex life during pregnancy. If you’re not having sex, then your relationship is going to suffer somewhat. And you also don’t want to blame this on the baby. At the very least she could allow you to have intercourse with her as she doesn’t have to be excited to help you relieve your frustrations. (And if you masturbate while looking at internet porn, I’m a little afraid that such behavior might become addictive). But maybe if she did participate, she might find that she would become excited. If she has any doubts as to safety, the two of you should talk to her doctor about this. It should be safe, but since you had to use fertility treatments, your doctor should be the one to give the OK, not me.