Gender Mistakes?

Alyssa • Enagaged to the love of my life and have a beautiful growing family. Im the mother of one beautiful 1 year old daughter. And currently pregnant with fraternal twin girls!! Due in September 2016

Hello everyone! So I'm 17 weeks 2 days with twins. We had our ultrasound today to see how babies were growing. And baby A they were having a hard time seeing the gender but they feel it was a girl. Same with baby B. But they also told me they are still small enough that things aren't "fully developed" to tell completely.

Has anyone had a change in sex from one ultrasound to another? I'm due for another Ultrasound in 3 weeks again at 20 weeks..

But my SO and I don't want to tell anyone and be wrong. Hah.

Has this happened to anyone else?