Foetus' face. Coloured 3-D ultrasound scan of a foetus' face. The foetus' left eye is at centre, with the nose and mouth slightly left and below it and its left ear at right. The material obscuring the right side of the face is foetal vomit. 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.