I don't know for sure, but when I was researching neem oil for my own skin issues, I kept seeing this disclaimer:
"Neem should not be taken by anyone (male or female) who is pregnant or trying to conceive.
It also contains compounds similar to those in aspirin and should not be used to treat children with fevers.
While people in some countries use neem oil internally, we definitely do not recommended taking neem oil in this manner.
Within those limitations, neem is generally considered to be one of the safest medicinal herbs available."
There are links here to some fertility-related studies:http://www.neemtreefarms.com/immune.html
I opted not to try it because we'll be TTC in about a year, and I didn't want to get myself "hooked" on a remedy that I might not be able to continue when TTC or pregnant.
IMO, I would shy away from it ... although I know it stinks to finally find something that is useful on your skin, only to find out it might cause fertility-related complications.