13 week NT ultrasound

Lauren • Tue, Mar 28 • Baby boy Nate born 10-07-17

Just had our NT ultrasound done. I'll be 13 weeks tomorrow. The sonographer made a gender guess for us and she said boy!! Between the legs there was a clear nub, but she said they can't 100% say until 20 weeks. So what do you guys think based on nub theory?