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Ultrasound use in New Zealand

Abstract:

Ultrasound is sonic radiation (as opposed to isotopic radiation of X-ray). A product of warfare, it was developed during World War I to detect submarines. Developed for obstetrics by Professor Ian Donald of Glasgow in the 1950s, by 1968 it was becoming a popular method of determining the growth of the fetus hiding in the amniotic fluid like a submarine skulking on the ocean floor (Oakley). Ultrasound is sound waves at frequencies over 20,000 per second - above the range of human hearing. The higher the frequency, the greater the power. Diagnostic ultrasound is done at a frequency range of 1-10 mega hertz (MHz). The irradiation (exposure) may be continuous (Doppler) or pulsed (imaging). A pulse generator passes a high voltage alternating current through a piezo-electric crystal, causing it to vibrate and emit ultrasound pulses. These are formed into a beam which penetrates the area interface. In New Zealand diagnostic ultrasound in pregnancy was in use from 1973. Radiologist J.H. Steward reported 20 to 30 scans per day at National Women's Hospital (NWH) with the number rising. However, the Maternity Services Committee Report 1976, "Maternity Services in New Zealand" (Bonham and Mackay) expressed some uncertainty about "the final place of ultrasound scanning as an alternative to radiology, particularly for the diagnosis of twins, placenta praevia and fetal head growth" (15.4). By 1980 NZ doctors were recommending that all pregnant women should be routinely scanned at 20 weeks "as a matter of course". Dr Florence Fraser, an obstetrician at NWH specialising in ultrasound took issue with this.

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pregnancy ultrasound, routine scans