Ultrasound Assessment of Umbilical Cord Morphology in the First Trimester: A Feasibility Study.

OBJECTIVE: The aim of this study was to determine whether morphology and measurement of the umbilical cord could be accurately assessed at the time of the 11- to 13(+6)-week scan.

METHODS: We conducted a prospective study of 100 consecutive women with singleton pregnancies at 11-13(+6) weeks' gestation who were seen for routine aneuploidy screening. Transabdominal ultrasound scans were performed, and the distance between two adjacent coils of the umbilical artery was measured in a free loop of umbilical cord. The antenatal umbilical coiling index (aUCI) was calculated as the inverse of this measurement (aUCI = 1/intercoil distance in cm). The maximum diameter of the umbilical vein was measured. Umbilical venous blood flow velocity was obtained using standard Doppler technique. Interobserver variability was assessed. A subjective assessment of the cord was performed using the Sepulveda system of classification to compare the reproducibility of the observations between two observers.

RESULTS: The intended measurements could be obtained in all cases. The aUCI was found to decrease with advancing gestation, while the umbilical venous diameter increased with gestation. The umbilical venous blood flow velocity also increased with gestation. Interobserver consistency in the objective measurement of the aUCI was poor (kappa 0.146). However, the Sepulveda classification system was found to be applicable and reproducible at this period of gestation (kappa 0.601).

CONCLUSIONS: Umbilical cord morphology can be consistently studied in the first trimester. A subjective method of evaluation of the morphology may be a more reproducible technique until measurement strategies are refined and operator experience developed.