Hi Greg,
He should definitely tell his girlfriend now and not wait. SZ has a genetic component and they will have to be aware of the signs and symptoms if they decide to follow-through with having the child.
Most people with SZ are inclined to wait to disclose until there's a level of trust and intimacy and the relationship is moving towards exclusivity or marriage. Your son has been forced to disclose right now.
I believe it is the only thing he can do. He can't expect to continue a relationship based on a lie. And maintaining and keeping the omission of the truth in place is to me just like lying about something that is an important part of his life.
It is possible his child won't develop SZ; however, it's possible the child could. For that reason alone disclosure is the only option. She will be the mother of his child and needs to know.
Myself, if it were me, I would've told my boyfriend about my SZ before we got intimate if you know what I mean by intimate. Hey, your son did not and that was his right, his choice. Stigma still exists.
However, now he must tell.
Regards,
Christina