3 line sign?

Jasmine
Has anyone heard of the 3 line sign when it comes to gender? Yesterday I went to my 12 week ultrasound appointment and saw 3 lines and immediately thought boy but my ob was very hesitant. Then I called my aunt and told her and said that when the baby is a girl there will be 3 lines early on and that's how you can tell? Does anyone have any insight on this?