Ultrasound detection of nuchal cord prior to labor induction and the risk of Cesarean section.

Abstract

To investigate the ability of ultrasound to detect the presence of a nuchal cord immediately prior to induction of labor and the association of its presence with delivery by Cesarean section. A transabdominal ultrasound scan using gray-scale and color Doppler imaging was performed immediately prior to induction of labor in 289 women in a prospective study to assess the presence of a nuchal cord. The presence of a nuchal cord was classified as present, absent or uncertain. The outcomes of labor, delivery and the neonates were obtained from the patient notes after delivery. A nuchal cord was present at 18% of deliveries. The incidence was not affected by parity, fetal position or reduced amniotic fluid volume. The sensitivity of ultrasound in diagnosing a nuchal cord was 37.5%, with specificity, positive and negative predictive values of 80%, 29% and 85%, respectively. The presence of a nuchal cord did not significantly increase the risk of delivery by Cesarean section (35% vs. 28%; relative risk = 1.22; 95% CI, 0.80-1.87), instrumental delivery for fetal distress, an abnormal cardiotocograph in labor or at delivery, an Apgar score < 7 at 1 min, arterial cord pH < 7.1 or neonatal unit admission. The sensitivity of the ultrasound diagnosis of a nuchal cord is low prior to induction of labor at term. A nuchal cord does not appear to increase the risk of Cesarean section or of poor neonatal outcome. The low ultrasound detection rate of a nuchal cord limits its use in decision making prior to induction of labor in high-risk pregnancies.