At the 20 week scan my nephew had markers for downs syndrome but they couldn't confirm it at that point in the pregnancy. My SIL spent the next 20 weeks of her pregnancy reading up and preparing for the possibility of having a DS baby. He doesn't have DS but my SIL said she would do the test if she was to have any more because the stress and worry was awful. She said it was the not knowing that was the worst part of it all.
I wouldn't go behind DH's back but I'd definitely be talking to him about it and trying to find a common ground.