I didn't know with my first. I had a feeling all along that it was a boy and I had a girl. With my second one, I had alot of problems and was having a sono every week at the end. Like Tallulahbaby, I looked at the monitor and knew instantly it was a boy. I didn't tell my husband though because he still wanted to be surprised at delivery. If I ever have another, I think I'll find out. It was fun shopping when I knew exactly what to buy.