When a fetus has the umbilical cord wrapped around his or her neck, it is called a “nuchal cord” — from the Latin word for “neck”. The cord can also be wrapped around another body part, such as the hand, foot, trunk, or perhaps even all of these. A nuchal cord is usually not a problem, being present in perhaps a quarter or even one third of all births; but sometimes it can cause a problem.
In combination with a short cord, it can prevent the baby from being born — for example, if the placenta is at the top of the uterus, and the cord loops around the baby’s body and then wraps his or her neck so that there is no extra length of the cord, the baby may literally be trapped in the uterus. It’s not common for this to happen — most babies even with nuchal cords wrapped two or even three times, or with body entanglements, can still be born vaginally, because the length of the cord allows it; but sometimes they just can’t (perhaps the baby is entangled in the cord too close to the placenta, or the cord loops over his body from shoulder to groin and back again). We’re all glad of intervention being available in these cases. [I even read of one woman who normally chose unassisted birth having a strong feeling that she ought to have a C-section with her current pregnancy, and when the baby was born by C-section, the cord was so super-short that they had to cut the cord to get the baby completely out of her uterus — obviously, this sort of problem is also super-rare! I also read of a woman who discovered that the umbilical cord was between her baby’s head and cervix, so in the weeks leading up to birth, she talked to the baby and asked him or her to hold onto the umbilical cord and keep it out of the way so it wouldn’t cause problems (such as umbilical cord prolapse); when the baby was born, s/he was holding the cord, just like the mama had asked. Coincidence? You decide.]
Here is an article for your files — an editoral from an ultrasound journal in 1999 which discusses research into nuchal cords. Whether you agree with everything that is in there or not, the bibliography is valuable for naming other studies that have been done, which is why I’m keeping it, in addition to the interesting discussion. [Sometimes links to Wiley InterScience don’t work right, so you can find this article by looking in Ultrasound Obstet Gynecol 1999, volume 14, issue 1.] And this article differentiated between tight and loose nuchal cords, finding that tight nuchal cords were associated with adverse outcomes at a much higher incidence than either loose nuchal cords or no nuchal cord.
Of course, not all articles noted significant differences with nuchal cords versus no nuchal cords (not sure if they distinguished between tight and loose, but that seems like a no-brainer to me to do that), so the jury is still out as to whether nuchal cords and entanglements cause statistically significant problems for babies; but it is also understood that nuchal cords can cause problems with certain babies. After all, if one baby out of a million dies before or after birth because of a nuchal cord, but the rest of the up to 37% of babies with nuchal cords are just fine, then it’s not statistically significant. But it is very significant to the parents of that baby who died.
Another confounding factor is the type of nuchal cord. It can be “sliding” (Type A) or “locked” (Type B); other sources distinguish them as “wrapped” (Type A) and “hitched (Type A). Type B is assoicated with a higher rate of complications with the baby, because it can tighten around the baby as the baby moves (I’m picturing a necktie or a noose, but may be a little off on that), but even this does not automatically require a woman to have a C-section (but if it is known beforehand, it would seem prudent to me to be more vigilant during labor, as well as in the weeks leading up to it).
Nuchal cords that are identified prenatally can resolve spontaneously, so if you have an ultrasound and a nuchal cord is noted, you shouldn’t panic. Here is an abstract for a case study published in 2003. In short, the woman had a breech baby (at 34 weeks) that she wanted to try to have turned externally, so she wouldn’t have to have a C-section. When an ultrasound was done (at 36 weeks), it was noted that the baby had a double nuchal cord, so an ECV wasn’t done. Two weeks later, an ultrasound showed that the nuchal cord was gone, so she was given an ECV and went on to have an uncomplicated vaginal birth. [This could also be a reason to decline a scheduled C-section due to breech, because babies can be turned, or can turn spontaneously, in just a few minutes, thus avoiding a C-section entirely… assuming you can’t have a vaginal breech birth for whatever reason.]
So, to sum up:
- many babies have nuchal cords, and it is usually no problem (my firstborn had a loose nuchal cord, and it was no big deal)
- nuchal cords can resolve spontaneously
- occasionally nuchal cords and cord entanglements can cause a problem, either with compromising the flow of blood between placenta and baby, or by strangling the baby (yeah, I know, the baby doesn’t breathe through the throat, but blood still needs to get to the brain through the neck — think Vulcan death grip or whatever — lack of oxygen to the brain can be either due to not enough oxygen in the blood [either due to breathing in the born, or placenta in the unborn], or to not enough blood to the brain [due to something wrapping too tightly around the neck, constricting the carotid arteries, whether in the born or the unborn]), and this can take place prior to labor or during labor, so women need to be aware of fetal movements, and particularly do fetal kick counts
- nuchal cords seem to be associated with more fetal distress or abnormal fetal heartrate patterns during labor and also cerebral palsy, although not all studies reached that conclusion (possibly due to failure to distinguish between tight and loose nuchal cords)
- nuchal cords may also play a role in some babies having difficulties during labor and birth, including failure to descend, if the baby is wrapped up in the cord enough (not typical, but possible, and it does happen)
- the cord can wrap around the neck in two ways, with one being worse than the other and associated with more rates of complications including perinatal death
- also regular ultrasound may not reliably discover nuchal cords, but color Doppler imaging has a high reliability
- induction of labor is an independent risk factor for nuchal cord
Finally, fetal compromise can happen due to a number of reasons and nuchal cord is just one of them, so it is wise for all pregnant women to be aware of fetal movement and to get checked out should they note a significant decrease in movement. It could save your baby’s life.
Filed under: labor and birth, pregnancy | Tagged: baby, birth, cerebral palsy, morbidity, mortality, neonatal death, neonatal loss, nuchal cord, perinatal death, perinatal mortality, pregnancy, pregnant, stillbirth, umbilical cord |