I would question everything in his diet and medications because if this has happened to him before, it is possible it's something to do with his sperm. The father is 50% of what is going on with any fetus. I would definitely have him go in for a sperm analysis. Especially since you have had two normal pregnancies before this. Not to say that miscarriages are uncommon, but three in a row would give me pause in light of his history. It's worth a shot anyway. Even if this one progresses normally its still good to find out if anything is going on with him. Good luck!
Oh wow, I'm sorry for your losses. I'm not an expert, but I do think it's unusual for m/c to be caused by something in the father's genetics. Maybe a combination of the two parents, but I'm not sure. Have they done any testing/bloodwork as a result of your three losses? I recently had my third m/c, and my doctor offered genetic testing at that point. (I don't have the results yet.) I do also have 4 healthy kids, too, so I think it is probably just one of those infortunate things with no particular cause. Good luck to you. Praying that things will go perfectly this time.