The correlation between ultrasonic manual and automatic measurements of foetal head and abdominal circumferences

To assess the correlation between ultrasonic manual and automatic ellipsoid measurements of foetal head and abdominal circumferences.

This comparative cross-sectional study was conducted at the Ultrasound Clinic, Karachi, from January to July 2004. Seventy two normal pregnant women with gestational ages between 14 to 38 weeks were included. Foetal head and abdominal circumferences were measured by manual method using traditional formulae and by automatic ellipsoid mode incorporated into the real-time ultrasound machines (EcoCee and Power Vision, Toshiba, Japan) using convex probes of 3 and 4.2 MHz frequency. Three readings of each parameter i.e. head circumference (HC) and abdominal circumference (AC) were taken by both methods. Mean values were calculated and compared using paired sample 't' test to assess the correlation between ultrasonic manual and automatic ellipsoid measurements.

The mean HC measured through manual method was found to be 20.11 +/- 7.04 cm and was significantly different from that of 19.46 +/- 6.82 cm measured through ellipsoid automatic technique. There was, however, a perfect positive correlation (r = 0.999) between these measurements. In case of AC, there was no statistical difference between the mean values obtained by the manual technique and those measured automatically (16.79 +/- 6.24 vs. 16.74 +/- 6.11; p < 0.44), correlation between these measurements (r = 0.997) was also significantly positive.

Correlation was found between the mean measurements of the foetal HC and AC by the manual and the automatic method of calculation; and even stronger for the latter. The automatic mode of measurement is a more rapid method than the manual calculation, and its use may be encouraged.