HI!
If you were my patient, I would advise you that this happens ALL THE TIME!
Ultrasound isn't perfect and often babies are not very cooperative. When you go in for your next one, the baby might feel like showing off for you so that you could get the best two out of three. I would suggest saving tags on your clothes too! =)
Dr B
That happened to my sister. But they told her she was having a girl and then when she had the baby it was a girl. At least they caught it early. It could have been how the baby was positioned.