Anyone have an elective ultrasound done to find out the gender early on?

I found a place that will let you go at 15 weeks to find out the gender, if baby is in a bad position or they can't tell, you can come back the following week free of charge.

I did book it, I'm super impatient this time around! Just wondering what your experience was if you had one done.. Good and bad!

I'm expecting that if its a boy it will be pretty easy to tell by then, but Ive heard some stories of people being told girl, when it's really a boy.