Pumpin here - blowin' up this thread lately! LJ, I just wanted to say, I don't think there is anything naive at all about not researching this more.
When I was pregnant with my first, my first OB (the one I went to for pregnancy confirmation but didn't return) presented all of the tests as standard, like the GD test or blood draws. He just said: "you'll see me every 4 weeks during the first trimester, at 12 weeks you'll need to schedule X, and at 15 weeks, Y..." etc. I barely realized I could opt out. I left his care for another reason but my second OB made a much more careful explanation of all of the tests and presented them much differently, like "there are a number of genetic screening tests available to you if you are interested in taking them, and we should talk a little bit about what each test covers and what the results might mean if you decide you are interested..." He was not discouraging at all, in fact he urged me to at least meet with the genetic counselor to discuss the pros and cons, but ultimately it was 100 percent different presentation from the first doc. I think it's great, when pregnant, to do a ton of research for yourself but at the same time, the burden should not be solely on a woman of any age to sit there and do independent medical research for every test that comes along; instead our providers should explain them well and make an effort to help us understand. Rant over...! But I think you have to just take this in stride. Given the 1. inordinate high false positive rates of this test 2. uncertainty of "elevated" risk anyway and 3. near certainty that they're using an inaccurate gestational age, then you should probably feel pretty confident that your results are just about meaningless. I'm a born worrier, but I would probably NOT be worried (given all of that), in your shoes. I know you don't really know me in person, but if you knew what a worrier I am, you'd see that as the reassuring statement I mean it to be!
Last thing: pretty sure that M21 is covered by insurance for anyone at higher risk for a chromosomal abnormality, and your test result would put you in that covered category. That said, I can see where your DH is coming from. Maybe you could call back the genetic counselor and make sure they know that your due date is questionable at best and see if she can reevaluate the numbers based on new info?
To everyone else: There is a prenatal yoga in my neighborhood (Brookland) on Tuesday nights. I'm thinking of signing up although I think I've mentioned I've never actually done yoga before

. Anyone up for joining? I could link to the info.