Early Gender Ultrasound Accuracy? 😬

Tracy 💖 • Daughter 8/11/16🎀 Twins due 10/17/18 🎀🎀
So I had an ultrasound at 16.5 weeks at an elective ultrasound place, and the technician confidently said "girl". When I asked if she was sure, she said "if they hand you a boy in the hospital, give it back- he's not yours"! The three white lines are there, I'm just wondering if that was too early. Now that my 20 week anatomy scan is Friday, I'm nervous that she was wrong (after we announced to our family & friends already). 😬