- Should we screen for nuchal cord using ultrasound when a woman is planning a vaginal breech birth? and
- What should we do with the information if we do identify a nuchal cord on ultrasound?
‘Nuchal cord’ means that one or more loops of umbilical cord are wrapped around the baby’s neck, during pregnancy or birth. Checking for nuchal cord prior to external cephalic version (ECV) or during risk assessment prior to a vaginal breech birth (VBB) is both common and controversial.
What is known:
- Nuchal cords are common, especially for breech presentation. For example, in this study (Wong & Ludmir, 2006), where someone specifically looked for a nuchal cord prior to an attempt at ECV, 34/75 (45.3%) babies were spotted wearing their cord as a necklace. They attempted the ECVs without this information. More babies with nuchal cords had transient (temporary) heart rate abnormalities, and their ECVs were less likely to be successful. But none of them had an emergency caesarean birth because of the way their heart rate was affected by attempting ECV.
- This really good summary of Nuchal Cord and Its Implications (Peesay 2007) indicates that at birth, as many as 30% of all babies could have a nuchal cord.
- It may cause problems in some pregnancies and/or births, but visual assessment by ultrasound does NOT help us to predict which ones. (… in general. Unless, as in this paper by Hinkson et al 2019, there are 6 loops of nuchal cord visible. Wow!)
What is not known: Does a nuchal cord increase the risk associated with an ECV or vaginal breech birth? We just don’t know if, or by how much, presence of a nuchal cord increases the risk. This is one reason neither of the RCOG guidelines (ECV, Management of Breech) indicate nuchal cord should be identified, or used as an exclusion criteria, for either of these. In fact, they don’t mention ‘nuchal cord’ or ‘cord around the neck’ at all.
When there is clinical uncertainty, we just say … there is clinical uncertainty. We can’t guarantee it won’t be a problem, but we have no clear evidence that it is likely to cause a problem.
Other guidelines often do say something like, “exclude nuchal cord.” This means, “Look for it with ultrasound to make sure it isn’t there.” But it’s not clear what one is supposed to do if you identify it IS there. And if a clinician has not looked for it, or has not spotted it, and it ends up being there and causing a problem during birth, have they been negligent? It’s a slippery slope.
In my own clinical experience, breech babies born vaginally quite often have one or sometimes two loops of nuchal cord around their neck at birth. My gut feeling is that these babies more often needed help to flex the head, for example with a shoulder press, but that this was not more difficult than when the cord is not there.
I also checked our video study (Reitter, Halliday & Walker 2020) database of 42 breech births with ‘good’ outcomes. Among these, 8/42 (19%) had a cord wrapped at least once around the neck. Among these 8, 5/8 had help with the arms, and 6/8 had help to flex the head. This was slightly higher than the overall averages in the whole dataset. In the dataset, there were also 2 cases of leg entanglement, 1 case of arm entanglement, and 1 cord prolapse, where the cord comes out first.
It seems plausible that cord entanglement, whether around the neck or another body part, could interfere with the normal mechanisms of a vaginal breech birth. These babies may then require more assistance to be born safely, which is not itself a problem, as long as that assistance is provided in a timely fashion. It also seems plausible that in some case, a tight or short cord entanglement could cause problems that would put the baby at risk. But the kind of potential problems Peesay describes are all very likely to be picked up with the kind of close monitoring (growth scans, fetal heart rate monitoring, etc.) that every known breech baby received antenatally and/or in labour.
I’ve also added a ‘cord’ tag to several videos in our video library. If you’ve taken our Physiological Breech Birth course, you can search the library to watch several videos where cord entanglements feature and are resolved.
In summary, these are my recommendations:
- Don’t routinely go looking for a nuchal cord in otherwise uncomplicated pregnancies.
- If you do spot a nuchal cord, explain the clinical uncertainty with regard to its implications.
- Offer and attempt ECV if the person chooses this.
- Offer and support a VBB if the person chooses this.
- When attending a VBB with a known/suspected nuchal cord in labour:
- interpret fetal heart monitoring in light of this;
- interpret descent in light of this;
- anticipate the cord could interfere with the mechanisms, which may require your assistance; and
- review all of your tools for assisting the head to flex.
I’d love to know others’ thoughts and experiences?