I do not really know much on this subject, but I have read on here that quite a few parents do have tests, just to ensure that everything is in order.
I'm sorry that I can not give you more info, but maybe you should ask your doctor about tests that are available for your husband and yourself.
All the best.
At least for the second child, if a chromosomal analysis was performed (karyotyping) and it did not show an extra 21st chromosome, then it could not have been Down Syndrome. I think that genetic screening for both of you is a good idea though to help rule out other potential problems.
By the way, my younger brother was born with Downs Syndrome and he was the greatest gift to our family. We adored him and he had so many wonderful qualities, including great courage. When he was 18 he was diagnosed with leukemia and he was sick until he died just after his 25th birthday. You can read more about him at
We miss him terribly.