they have never heard of MaterniT21 AND they are iffy about progesterone testing? If you have the option I'd look for a new dr., honestly.
My Dr. said that she was iffy on the MaterniT21 becuase they have a high-ish rate of false positives and then you end of getting amnio anyway but have wasted time and money. But, that is IF you get a positive. And, she was down on it for me since my odds were very very low anyway and she felt it was not worth it. Again, for me with my history. However, for the peace of mind it might bring in this situation I would seriously consider it.
So, things to consider!
And any genetic councilor should absolutely have the details on it for you!