Foetus. 2-D and coloured 3-D ultrasound scans of a foetus' face. The 3-D scan shows the foetus more clearly. The chin is at centre, a hand is at right centre and the umbilical cord is at lower 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.