The effect of vascular coiling on venous perfusion during experimental umbilical cord encirclement

The aim of these studies was to compare venous perfusion in umbilical cords subjected to a standardized tight encirclement force. Comparisons were made between cords from normal pregnancies and those complicated by gestational diabetes mellitus and intrauterine growth restriction.

The cannulated cord segment was wrapped around a plastic container, which in turn was attached with nylon string to a hanging graduated measuring cylinder in which known volumes of water could be applied for weight. The cord was perfused with Krebs solution to a constant venous perfusion pressure of 40 mm Hg. Weights of 100-g increments were applied until total cessation of venous perfusion was observed. The weight, length, number of vascular coils, and degree of hydration were recorded for each cord. The coiling index was defined as the number of vascular coils per 10 cm of cord.

Regression analysis of 34 cords (normal, n = 16; gestational diabetes mellitus, n = 12; intrauterine growth restriction, n = 6) identified a significant inverse correlation (P =.0003, Spearman rank correlation) between coiling index and the minimum weight required to occlude venous perfusion. Cords from pregnancies complicated by intrauterine growth restriction displayed a higher frequency of vascular coiling and were more easily occluded (median weight, 350 g) than were cords from pregnancies complicated by gestational diabetes mellitus, which were less coiled and tended to resist occlusion (median weight, 1100 g).

During experimental cord encirclement there was a significant inverse relationship between vascular coiling and susceptibility to cord venous occlusion when traction was applied to the encirclement.