winter I am one who doesn't agree with your opinion, which I see on here all the time. Your suspicion that I haven't thought it through is wrong: it's because I have thought about it a lot that I have decided that it's much, much more complicated than a simple question of bodily autonomy for the woman. The answer will depend on each situation, and will often be unfashionable, but will never - to my mind, anyway - clash with any feminist ideal either. Life is never as simple as your straightforward answer, and pregnancy is a 9 month period of time when it is even less simple.
Going back to the OP, your set-up and this argument with your DH sounds much like mine with my DH and the sorts of things he comes out with. I regularly hear about how we always end up doing what I want (well yes, because otherwise we just wouldn't be doing anything), and how I railroad him to get my way (no, his arguments are just never as well researched or thought through). So, inevitably, I hear about how it would be nice if "just once I could have my way". To which I ask what is more important here: you getting your way or us doing the right thing? And I generally forge ahead, and 99 times out of 100 he ends up agreeing with me (after some time).
I have learned to just quietly get on with things while being sensitive to his wishes and absolutely hand over decision making where I don't have a strong view. But the big ones (where we live, school choices) I did what I knew to be right for all of us and he caught up. My DH has the good grace to say when he was right/wrong, and we are evolving as a couple.
Also, I would add that this whole 'surprise' thing I've always found odd. It would be a surprise if it came out and was a cat! You KNOW it's going to be a boy or a girl - you can try imagining both. There are only two permutations! Also, 16wks is probably on the cusp of feeling the baby's movements. Give it a fortnight and you will feel them properly. It might help. Finally, you're not at the half-way point yet. There's no urgency is there? Maybe wait a bit until things have calmed down between you. Go for the scan, ask the sonographer to write it down on a bit of paper in an envelope, put it away until the dust has settled. Just some suggestions. Find out if you wish to, but it might be an idea to give it a little time to let the argument subside.