The scans use the same technology as the more traditional 2D ultrasound scans but do not take a single image and instead they take multiple images whcih are processed quickly in a powerful computer to create the 3-D image that is projected to you.

As such, they are just as safe as the traditional 2D scans that have been used to scan pregnant women  for 30 years and there is still no evidence to suggest that they cause harm to either party.