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Ectopic pregnancy. Coloured 3-D ultrasound scan of a 7-week-old ectopic pregnancy in a Fallopian tube (oviduct). The developing embryo is the circular structure at far right. The ovary, from which the egg (ova) was released into the Fallopian tube, is at centre left. In an ectopic pregnancy the embryo implants outside the uterus, usually in an oviduct. It is a life-threatening condition which requires the immediate surgical removal of the foetus. Ultrasound is a diagnostic technique that sends high-frequency sound waves into the body via a transducer. The returning echoes are used to build an image of an internal structure. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR NAJEEB LAYYOUS)