Finding gender at first blood draw

Amy • Mon, Jul 23 • Mom to 4 beautiful girls. 3/3/10, 4/27/14, 4/8/17, 3/7/19.

I’m having my 4th little and I would love to try and know the gender for the baby with the blood drawn but I’ve never done it before. Do you just ask or how does that work? Also how accurate is it?