The main point of the scan is an anatomy check, to make sure all the pieces are developing correctly. I think of it as a live baby check. For most women though, this is the gender check scan. I'd like to know too, but I'm thinking that gender confirmation is way way down my priority list below alive and healthy.
So, you are on notice that this is your last chance for wild gender predictions. In the spirit of fairness I will tell you that I believe there is something like a 90% chance that the fetus is male. Not that I would not be absolutely crazy about having a little girl, since I could make this for a little girl, it's just my honest opinion of the odds.
You see, I think that in some families, a gender bias is inherited through the male line. Some men just seem to produce more of one type of sperm or something to that effect. Take my own family. Women run in my family. Those of you who know my maiden name know no one else with that last name who is not a close relation of mine. Back in the early days of the web when I had a web page with my full name on it, I would occasionally get emails from Australia or New Zealand because someone there had the same last name and was just so thrilled to find someone else with that name. It's just that rare. A while back a woman in Canada was doing a study on the name and compiled a detailed family tree on four different families that had the last name, going back three centuries. She sent to to my Dad (having contacted him earlier as part of her research). When Dad looked over the trees he said "That's a lot of girls." And so it was. You will note that my only sibling is also female. Warren's family is the same way, only with boys. Warren's only sibling is a brother who has two sons. Their father had six or seven brothers (I keep forgetting which) and only two sisters. I'm sure someone will try to lecture me on statistics and how if you're flipping a coin you can have long runs of either heads or tails in a small sample size. This is true, and it would be nice if it were true for Warren's family since I'm sure both sets of grandparents would welcome a granddaughter for a change. On the other hand, it does not disprove the gender bias is possible, and in my Dad's line there is no way you can argue with me that it does not exists. You don't get that many girls in four different branches going back centuries without a bias (and yes, kids who died in infancy were included, so the fact that girls survive better as infants was not the source of the bias). So, I'm expecting the fetus to be male, but any news is good news on the gender front is unimportant compared to the news I hope for on the health front.