Are the international ultrasound reference standards appropriate for Iranian fetuses

The article describes the development of ultrasound tables for biparietal diameter (BPD), femur length (FL), abdominal circumference (AC), and head circumference (HC) for fetuses in Iran. It was attempted to determine if racial differences exist between Iranian and Australian fetuses in ultrasound measurements of BPD, HC, AC, and FL. The sample for this study consisted of 70 Iranian and 93 Australian pregnant women. The Iranian women received prenatal care and delivered at Fatemieh Hospital in Shahrood, Iran during October 1998 through February 1999. All these women had an ultrasound scan for anomalies in the second trimester. We selected only those pregnancies in which the estimated date of delivery by last menstrual period was within +/-14 days of the estimated date of delivery determined by the initial ultrasound examination. The data from Australian fetuses were obtained from the ultrasound section at the Wollongong Hospital in Australia. Birth weight differences were observed, with Australian infants being heavier than Iranian infants. The results also showed Australian fetuses have longer FL and larger HC, AC, and BPD than Iranian fetuses in the third trimester. Overall, this study shows that race-specific standards for estimating gestation age (GA) may be an important consideration in improving the accuracy of ultrasound estimation of GA. Because the evaluation of retardation growth retardation is so dependent on GA, assessment using standards specific to the Iranian race may more accurately classify infants and improve the prenatal diagnosis of fetal growth disturbances. Using European or Australian standards may cause overestimation of the rate of growth-retarded fetuses in Iranian pregnancies.