I finally got a call today from my doctor's office with the results of the ultrascreen from St. Joe's Hospital. According to the results, I have no greater or lesser chance of having a Down's Syndrome baby than what is usual for my age (which is about a 1 in 400 chance). So good news, but it doesn't completely rule out the possibility. We'll be able to see more at the 20-week ultrasound towards the end of April.
If you scroll to the very bottom of the page, I set up a counter so you all can see where I am as far as weeks/days. Not quite halfway yet!