Sonographic Estimation of Umbilical Cord Cross-section Area and its Reference Value in Normal Pregnancy

Introduction: The routine antenatal sonographic investigations of the umbilical cord are limited for assessment of number of umbilical vessels and doppler evaluation of umbilical blood flow. With the advancements of the sonographic techniques it is now possible to have more detailed evaluation of umbilical cord. There exist only few literatures on assessment of umbilical cord cross-sectional area during pregnancy to provide a baseline reference value. Aim: To establish the reference intervals of cross-sectional area of the umbilical cord during gestation and to find the correlation of umbilical cord cross-sectional area with the foetal anthropometric measurements. Materials and Methods: This study was conducted among 214 normal pregnant women who underwent a routine antenatal sonogram during gestational age ranging from 24-39 weeks in the Department of Radiodiagnosis. The umbilical cord crosssectional area was calculated at a plane immediately close to the umbilical cord insertion to the foetal abdomen. The following foetal parameters were studied: Biparietal Diameters (BPD), Head Circumference (HC), Abdominal Circumference (AC), Femur Length (FL), and Estimated Foetal weight (EFW). The relationship between foetal anthropometric measurements and umbilical cord cross sectional area was assessed using spearman rank correlation. The 5th, 10th, 50th, 90th and 95th percentiles of umbilical cord cross-sectional area were calculated for each gestational groups using polynomial regression analysis. Results: A statistically significant correlation was observed between cross-sectional area of umbilical cord with both gestational age and foetal anthropometric parameters. The mean age of study population was 25.08±3.5 years and the mean gestational age was 34.42±2.5 weeks. We observed a strong correlation between head circumference and umbilical cord cross-sectional area. Conclusion: The mean umbilical cord cross-section area increases steadily with gestational age for up to 34 weeks and then it declines. Umbilical cord cross-sectional area can be easily measured and hence it can be included in routine antenatal sonographic evaluations to predict the perinatal outcome. Careful monitoring of the pregnancy is needed in case of abnormal cross-sectional area measurements.