It will also tell us, definitively, if it's a boy or a girl. I'm pretty sure a lab is involved so we're not going to walk out of the office with an answer, but will know in a few days or a week.
Thankfully, we don't live in the general area of any chemical plants, but a couple of other things have pointed to us maybe having a girl. First, there's the fetal heart rate: if it's above 140 you're having a girl; below 140 for a boy. Ours was at 164. However, this old-wive's-tale has been scientifically disproven. (Google "fetal heart rate boy girl" for details.) Then, there's this article about mom's calorie-intake at the time of conception. The Mrs. was watching the calories with her friend, JC, at the time.
Also, a friend and our tax accountant (self-determined 90% correct guess rate) have said it will be a girl. And even though I'm the first son of a first son, Pam is the first daughter of a first daughter of a first daughter of a first daughter.
People have already been asking if we want a boy or a girl. I myself asked this question of a former brother-in-law once and received the answer, "A healthy baby." I never forgot that and so it's become our answer (see paragraph 1 of this post). But after that, we divide along gender lines--Pam says girl, and I say boy.
So, what will it be?