Assessment of umbilical cord coiling during the routine fetal sonographic anatomic survey in the second trimester

The purpose of this study was to evaluate the sonographic accuracy to determine the umbilical coiling index (UCI) during the routine fetal anatomic survey in the second trimester.

In 300 consecutive women with singleton pregnancies and absence of gross fetal anomalies who had a routine second-trimester fetal anatomic survey, a distance between 2 pairs of coils was measured from the longitudinal images of the umbilical cord, and the antenatal UCI (aUCI) was calculated. The aUCI was compared with true UCI results obtained after birth.

Two hundred thirty-six patients had adequate sonographic umbilical cord images, and all required demographic, antenatal, and labor data collection to meet the inclusion criteria. A statistically significant correlation between aUCI and true UCI was found (P < .0001; r = 0.643). The mean aUCI was 0.402 (80% confidence interval, 0.382), and the true UCI at birth was 0.203 (80% confidence interval, 0.176). The sonographic evaluation showed 12.3% and 8.9% of hypocoiled and hypercoiled cords, whereas evaluation at birth found 10.6% and 8.1% hypocoiled and hypercoiled umbilical cords, respectively. The sensitivity values of sonography to predict hypocoiling and hypercoiling at birth were 78.9% and 25.4%, respectively.

A sonographic evaluation of umbilical cord coiling in the second trimester correlates with the true UCI at birth, although the sensitivity in predicting coiling patterns as hypocoiled and hypercoiled cords is less accurate. A difference between the aUCI and matched UCI at birth could be explained by a sonographic error in the sampling of different umbilical cord segments with discordant coiling patterns or the possibility of a dynamically evolving UCI with advancing gestational age.