Hypospadias is a birth defect in which the urinary tract opening is developed on the ventral surface (under side) of the penis rather than at the tip of the penis. This happens when there is no type II 5-alpha reductase enzyme in the male embryo. As finasteride inhibits this enzyme, the result could obviously be the same. In truth, you have no worries and no need to get off. Do some research and you'll find animal studies where massive doses were administered IV to pregnant animals w/ no effect. The very infinitesimal amount, if any at all, your wife could receive via your semen during intercourse, or even handling broken pills, while she's pregnant will not cause your baby any problems. The extremely small amount, again if any, that she would/could receive during conception is also a non issue. External genitalia does not undergo developmnent until 7-9 weeks gestation. Do your own research and speak w/ her OB/GYN. I don't like finasteride for several reasons & would never use it again personally, but this concern is not one of them. If it still makes you uncomfortable, just get off when she conceives.
Rex.