Foetus. Coloured 3-D ultrasound scan of a foetus with its umbilical cord around its neck. The umbilical cord is at lower left, then wraps around the back of the foetus' neck and is seen again at upper left. Ultrasound scanning is a diagnostic technique that sends high-frequency sound waves into the body via a transducer. The returning echoes are recorded and used to build an image of an internal structure. Foetal ultrasound scanning is routine during pregnancy. 3-D scanning uses computer technology to return more detailed images than conventional 2-D scans.