Improving Sonographic Evaluation of the Umbilical Cord at the Second-Trimester Anatomy Scan

Current guidelines for second-trimester sonographic examination recommend evaluation of the fetal anatomy and growth, placental location, and amniotic fluid volume and examination of the umbilical cord by trained sonographers.(1,2) Umbilical cord assessment is routinely limited to the cord vessel number because a single umbilical artery is well established to be linked with poor pregnancy outcomes.(3) However, a substantial number of obstetric complications may arise from other conditions involving the placenta and umbilical cord.(4,5) Indeed, a poor perinatal outcome has been associated with other characteristics of the umbilical cord, such as being thin,(6) having a velamentous insertion,(7) and abnormal coiling.(8,9) We report die practice of a systematic approach to the assessment of the umbilical cord during the second-trimester anatomy scan and propose a new sonographic classification system of umbilical cord coiling. Our method assessed the following 4 characteristics of the umbilical cord: 1. Evaluation of the number of vessels-The umbilical cord was imaged in cross section and magnified to visualize the number of vessels. If the vessel number was uncertain because of suboptimal views, color flow imaging of the intra-abdominal vessels running alongside the fetal bladder was available to confirm the presence of 2 umbilical arteries.(3,5) 2. Measurement of the umbilical cord area-To assess the amount of Wharton jelly protecting the umbilical vessels, a mid segment of the umbilical cord was visualized in cross section, and the area was measured using the software of the ultrasound machine (Figure 1). These measurements were then compared with an established umbilical cord area nomogram.(10)