Hi Jim 19-79, I guess it is really crucial how you communicate that bit of information, maybe you can not disclose it until they see how nice and balanced you are and a great catch, and start liking you? If you potentially can have a relationship, then it doesn't matter much if you haven't had one before.
A long time ago I had a longish relationship (let's call it like that) with this guy, 32, who never really had a real relationship before, and it was a nightmare not because he never had relationships before but because he was a jerk (starting fights, yelling, threatening suicide to obtain what he wanted, etc), and almost 10 years later I hear he still does the the same to all his girlfriends.
So, it doesn't really matter how many girlfriends you have had, but if you are ready to have one.