Objective: To quantitate umbilical vascular coiling antenatally, and to correlate the coiling index with Doppler flow characteristics in umbilical vessels.
Methods: We studied 45 normal term fetuses within 24 hours before delivery. The umbilical coiling index was calculated using sonographic longitudinal views of cord vessels from several segments antenatally, and by dividing the total number of helices by the cord length (in centimeters) postnatally. Doppler flow velocities were obtained from umbilical arteries and vein in each cord. Flow characteristics were correlated with the umbilical coiling index.
Results: The mean (+/- standard deviation) umbilical coiling index was 0.44 +/- 0.11 in the antepartum period and 0.28 +/- 0.08 after birth. Regression analysis showed a significant linear trend (r = 0.71, P < .001). The correlations between sonographic coiling index and umbilical arterial Doppler flow characteristics (mean velocity, pulsatility index, resistance index, and systolic-diastolic ratio) were not significant. The sonographic coiling index was related to time-averaged velocity and flow in the umbilical vein. A good correlation was found between umbilical vein flow and the coiling index, with a significant linear trend (r = 0.59, P < .001).
Conclusion: An intrauterine umbilical coiling index can be determined by ultrasound and correlates well with the actual index at birth. The sonographic umbilical coiling index is related to Doppler flow characteristics in the umbilical vein.