Sonographic foetal measurements in a cohort of population of Karachi, Pakistan.

The purpose of this cross-sectional study was to establish reference intervals for sonographic measurements of foetal parameters in women with normal singleton pregnancies in a cohort of population of Karachi, Pakistan. It was conducted at the Ultrasound Clinic, and Ziauddin Memorial Hospital, Nazimabad, Karachi, from January 2003 to July 2004. The measurements of foetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) were carried out on commercially available ultrasound machines using a convex probe of 3.5 MHz frequency. Four hundred women were enrolled; 358 women completed the study. Mean +/- SD, reference intervals and 5th and 95th centiles for the foetal parameters were computed. Regression equations calculated were BPD = -0.36 + 0.27 x GA, (R2 = 0.97); HC = -0.96 + 0.05 x GA, (R2 = 0.95); AC = -0.345 + 0.33 x GA, (R2 = 0.95) and for FL = -1.50 + 0.24 x GA, (R2 = 0.97). [GA = gestational age in weeks, R2 = coefficient of determination]. In this cross-sectional study, predominantly of Urdu-speaking "mohajirs" (67.9%) the reference intervals of commonly used foetal parameters for assessing gestational age i.e. BPD, HC, AC and FL, were established. A larger, multi-centered study to encompass the different ethnic groups of the population is required.