Ultrasound Detection of Nuchal Cord Tension in a Simulated Nuchal Umbilical Cord Model

Background and objective Ultrasound assessment of nuchal cord tightness may help identify fetuses at increased risk of cord accidents. Our objective was to assess ultrasound detection of simulated nuchal cord tension. Methods This was an ex vivo pilot study of human umbilical cords harvested from discarded placentas. The simulator consisted of a plastic bucket with a 5.1-cm-diameter cylindrical crossbar to simulate a fetal neck, filled with water and covered with a membrane. Using ultrasound, we measured deformation of the wrapped cord loop at 0, 2, 5, 7, and 10 lb of tension, using each cord's off-tension free loop as a control. We used linear mixed-effects modeling to test the association of cord deformation with tension, accounting for cord characteristics. Results We evaluated 30 cords (mean length, 29.5 cm). Increasing tension resulted in increasing cord deformation between 0 and 5 lb, with no further deformation above 5 lb. The greatest deformation occurred between 0 and 2 lb, which was greater than the deformation occurring between 2 and 5 lb (p = 0.002). Cord length, days from delivery, and thickness were not associated with deformation. Conclusions In this proof-of-concept study, we detected nuchal loop tension using ultrasound in a simulated nuchal cord model, with the greatest deformation occurring between 0 and 2 lb.