My husband and I were told at our 20 week ultrasound that we were having a boy. The tech told us she was 100 percent sure that we were having a boy. How accurate is her statement. Is it safe to buy blue?

It's pretty safe to buy blue, but have some neutral colors as well. I have delivered girls that were supposed to be boys and 3 boys that were supposed to be girls. So, keep the receipts.

These estimates are usually pretty accurate, but unless you have a 3-D ultrasound there is always a risk of mistake.

I agree with J-9

Also, you'll probably have more u/s in the future and you'll be able to check again. ;)

If, after viewing a ultrasound, it is pronounced a boy, then it usually is. Although, obviously not always. If it is pronounced a girl, there is a slightly higher chance that it might actually be a boy.
I went along to my ex's ultrasound, after telling them I wanted it to be a surprise.
At one point, the nurse inadvertently said, "well, that's pretty obvious", which sort of gave the game away... and yes, it was a boy.
I guess that sometimes the nurse cannot see it clearly, they may think it's a girl, when its actually a boy, when they can see it, well, its rarely a girl, obviously.
Either way, you'll love them. Good luck, enjoy, and don't stress or take it too seriously...

In all my experience so far most of the "mistakes" are when the ultrasound tech tells a patient that it is a boy. I've seen more boys go home in pink than you could shake a stick at.