The term for an umbilical cord that passes around the fetal neck is nuchal cord. Reported prevalence rates at delivery range from 6% to 37%. Up to half of nuchal cords resolve before delivery. Although the diagnosis is not routinely made before delivery, it may be suspected if there are variable fetal heart rate decelerations on cardiotocography during labor. This study evaluated transabdominal ultrasonography for detecting a nuchal cord just before induction of labor. Another goal was to learn whether a nuchal cord during labor predicts an increased need for cesarean delivery. Scans using gray-scale and color Doppler imaging were done in a prospective series of 289 women having labor induced after 36 weeks gestation. Transverse and sagittal views of the neck were obtained, and nuchal cord was diagnosed if the cord lay around at least three of the four sides of the neck.
Postmaturity was by far the most common reason for inducing labor in this series. A nuchal cord was found in 18% of deliveries. Most often there was a single loop of cord. More than one loop of cord lay along the neck in 10 of 52 deliveries in which nuchal cord had been diagnosed. Ultrasonography was 60% sensitive with more than one loop present but only 37% sensitive with a single loop; the difference, however, was not statistically significant. Nuchal cord could not be related to reduced fetal movement before induction, parity, an occipitoposterior position, or a reduced amniotic fluid index. No significant increase in cesarean deliveries was associated with nuchal cord, and the condition did not predict low Apgar sores, admission to a neonatal intensive care unit, or the cord arterial pH. Neither of the two neonatal deaths was associated with nuchal cord.
In this series, the presence of a nuchal cord did not increase the risk of cesarean delivery and did not compromise the neonatal outcome. Ultrasonography does not reliably detect nuchal cord before induction of labor, limiting its value in high-risk pregnancies.