Why does the bladder have to be full before going to an ultrasound?
Seems like everyone else has covered the important bits… just in case you were wondering, your bladder needs to be full to push up your uterus enough that the ultrasound tech can be sure that the placenta isn’t covering your cervix, which would make a vaginal birth impossible. When I went for mine my bladder wasn’t quite full enough so she did everything else first, and by the time she got back to check I was so full I felt like I could have exploded, it was awful.
