A nuchal cord is also known as a cord around the neck of the fetus which occurs while the fetus is in the womb. Prevalence rates vary from 6% to 37%. The cord can be wrapped around the neck as little as one time, and I have personally seen a cord wrapped around the neck four times. The nuchal cord can be detected by an ultrasound prior to the onset of labor. The sensitivity of an ultrasound for detecting a nuchal cord is as high as 97% when the color doppler is used.
A nuchal cord can develop as a result of an unusually long umbilical cord and/or a very active fetus. An average umbilical cord length is 20 inches. The umbilical cord lengths, however, can vary from being totally absent (achordia) to being exceptionally long up to about 118 inches.
Whereas the existence of a nuchal cord can cause anxiety for the expecting parents, the nuchal cord is a condition which is common and usually will not interfere with the pregnancy. The delivering provider will merely pull the cord over the infant’s head at the time of delivery, thus taking care of the condition. On some occasions, the provider may have to clamp and cut the umbilical cord while the cord is still wrapped around the infant’s neck as the cord will be exceptionally tight. In this case, the provider does not want to use excessive traction to pull the cord over the infant’s head as this can lead to rupture of the umbilical cord. I know that this can be disappointing to the parents who are desirous of delayed cord clamping, but a tight nuchal cord that has to be cut when the infant’s head is delivered is not a good candidate for delayed cord clamping.
A hospital or a birthing center will usually employ continuous or intermittent fetal monitoring which will monitor the fetal heart rate. Sometimes, the delivery facility may choose to use intermittent fetal heart auscultation using a doppler instead of using continuous monitoring. If the nuchal cord is especially tight around the neck, the fetal heart pattern will show a condition known as variables. Variables will show up as a dip or decrease in the fetal heart rate when a uterine contraction ensues. This is caused by the fetus slightly descending when the contraction occurs which will pull on the nuchal cord. Remember that the umbilical cord is responsible for providing oxygen and nutrients to the fetus so that pulling on the cord can temporarily reduce the amount of oxygen and nutrients delivered to the fetus. A healthy fetus, however, will tolerate the slight decrease in oxygen and nutrients without issues.
If the nuchal cord is exceptionally tight, the fetal heart tracing may begin showing severe variable decelerations. In this situation, the provider may opt to preform a cesarean section as the fetal well being may be compromised. Again, however, the majority of nuchal cord pregnancies can be delivered vaginally without complications. A nuchal cord is not a reason for an automatic cesarean section.
Other complications such as preterm labor, premature delivery, premature rupture of membranes, and intrauterine growth retardation (IUGR) are not increased in pregnancies with a nuchal cord.
In a study published in the Journal of Perinatology in 2013, 200,000 births were followed where the nuchal cord prevalence was an expected 6.6%. The study concluded that extra labwork or extra monitoring based solely on the finding of a nuchal cord was not warranted.
Please feel free to contact me with any questions or comments. Wishing you a happy and uneventful delivery. Pablo