Conflicting views on certain things are ok. But kids is not one of them. 10 months is a long time, but 3 or 4 years from now will make it that much harder. It is definately something that needs talking about. If he is 100% sure, no doubt in his mind what so ever, and the same for her, then there is unfortunately only one solution. If, however, one of the two is"mostly" sure, that leaves room for "changing one's mind someday" and i'd say wait, "if" the relationship is worth it.
Now as for the dna test. It is more than likely a previous issue. I have a friend who everyone is convinced is paying for a kid that is not his. And he's too attached to the kid to find out the kid's not his. But future kids will be verified. Don't take it personal, guys like all people use experience as a guide. And sometimes it doesn't come out the right way. In fact, most of thetime it doesn't.
Good luck