Prenatal Diagnosis of a Nuchal Cord: Assessment of Test Accuracy and Determination of Clinical Significance

Abstract

We hypothesize that the imaging characteristics of real-time ultrasound and color flow mapping (CFM) would permit differentiation between a loosely applied or benign nuchal cord and a nuchal cord that was tightly applied to the fetal neck. We postulated that second-stage fetal complications would be significantly increased in the second group of patients.

In a cohort study, 83 patients referred for ultrasound fetal assessment were assigned to either a control group (n = 46, no cord detected with both real time and CFM), group 2 (n = 18, suspected loosely applied nuchal cord) and group 3 (n = 19, suspected tightly applied nuchal cord). Outcome parameters included the finding of a nuchal cord at delivery and the incidence of significant second stage of labor complications.

We observed that the incidence of second-stage complications was significantly increased in groups 2 and 3 compared to group 1 (P < 0.001), but we could not determine any significant difference between study groups. Antenatal test accuracy was calculated using two-way tables for both the finding of a nuchal cord at delivery and fetal distress in the second stage of labor: The positive predicted values for these variables were 76% and 68%, negative predicted values 83% and 60%, specificity 81% and 77%, and sensitivity 78% and 50%, respectively.

Key Words:

• Nuchal cord
• Fetal distress
• Ultrasound
• Color Doppler