Pregnancy ultrasound. Ultrasound machine and its screen display of a scan of an unborn child. A transducer (not seen) is being used to scan the swollen abdomen of a pregnant woman. The transducer emits high-frequency sound waves and detects the reflected echoes. The results are used to build this image of the developing foetus in the womb. This safe, non-invasive procedure is used routinely in pregnancy to assess the growth and health of the developing foetus. This is a standard anomaly scan, carried out when the mother is 20 weeks pregnant. The detection of a serious anomaly at this stage (halfway through pregnancy), allows surgery or a termination to be considered.