I've been getting my generic finasteride online for a while now. It's legitimate, the prescribers are UK registered, and I found it more convenient than going through my GP.
Everyone seems to get slightly different advice on this. I'd be inclined to check with your doctor or pharmacist before starting, especially while your wife is pregnant. It's probably better to be cautious and get advice that's specific to your situation rather than relying on anecdotal...