I've been taking Finasteride since January and just found out my wife is pregnant. Should I worry?

Your wife is fine as long as she didn't take the medication herself.  Please see an expert if you are concerned.  There are great alternatives like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

There is no good evidence anywhere in the published medical literature to suggest there is a problem for the children of men who use finasteride. 

There are multiple studies suggesting that men who take finasteride while their wife is pregnant have nothing to worry about as finasteride can't get to her through semen