How do the people in the hospital know if its a boy or a girl in the scans? (3D)?

its hard to see on some scans it depends if the baby is laying at a good angle ,, the scan technicians have had lots of practise but can still get it wrong ,the 3d scans are alot clearer than a normal one though,,,you may have seen the of the baby but as you say it could have been the cord so you will just have to wait and see until its born. :)