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Foetal heart. Coloured 3-D ultrasound scan of part of a human foetus, showing the heart (dark, upper left) and the descending aorta (down centre). The spine is the knobbly structure from upper right to bottom right. 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. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR NAJEEB LAYYOUS)