I didn't think u could

So my brother and his daughters mom aren't together any more and she's seeing someone else and has another baby on the way. She announced that she found out the gender of her baby at 12 weeks 3 days. Is this even possible? I know u can find out through blood tests but she said it was from ultrasound. I just don't wanna buy her anything for the baby and then it end up being the other gender