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|Classification and external resources|
A nuchal cord (/ˈnʲu.kəl/ occurs when the umbilical cord becomes wrapped around the fetal neck 360 degrees. Nuchal cords are common, with prevalence rates of 6% to 37%. Up to half of nuchal cords resolve before delivery.
- A "Type A" nuchal cord is wrapped around the neck 360 degrees.
- A "Type B" pattern is described as a hitch which cannot be undone and ends up as a true knot.
In 1962, J. Selwyn Crawford MD from the British Research Council defined a nuchal cord as one that is wrapped 360 degrees around the fetal neck. Dr. Crawford commented "It is all the more remarkable, therefore, that little work has been done ... to analyze its effects during labor and delivery". To date, there is no prospective case control double-blind study looking at nuchal cords and observational studies vary in opinion as to the degree of poor outcomes. Also not included in these studies is which umbilical cord form (of the 8 different possible structures) was considered a nuchal cord.
Ultrasound diagnosis of a cord around the neck was first described in 1982. “Coils occur in about 25% of cases and ordinarily do no harm, but occasionally they may be so tight that constriction of the umbilical vessels and consequent hypoxia result.” Williams Obstetrics 16th Edition, has only one single sentence in the entire textbook regarding cords around the neck. By contrast, the First Edition of the Encyclopædia Britannica from 1770 had 20 pages of information about Umbilical Cord Pathology with drawings of Umbilical Cord Entanglement. The Royal College of Obstetricians and Gynaecologists has these images on its brochure. There are currently three recent texts on ultrasonography which demonstrate the ability of ultrasound to identify umbilical cord issues with reliability as of 2009.
A study published in 2004 was done to establish the sensitivity of ultrasound in the diagnosis of a nuchal cord. Each of 289 women, induced the same day, underwent a transabdominal ultrasound scan with an Aloka 1700 ultrasound machine with a 3.5 MHz abdominal probe, using gray-scale and color Doppler imaging immediately prior to induction of labor. Presence of the cord was sought in the transverse and sagittal plane of the neck. A nuchal cord was diagnosed if the cord was visualized lying around at least 3 of the 4 sides of the neck. A cord was actually present at delivery in 52 of the 289 women. Only 18 of the 52 cords or 35% of the nuchal cords were detected on ultrasound done immediately before delivery, and 65% of nuchal cords were not detected. Of the 237 cases where there was no cord at delivery, ultrasound had false positive results, i.e. diagnosed a cord in 44 of the 237 cases (19%) in which there was no cord present at all. In this study, ultrasound was only 35% accurate at finding a single loop, and only 60% accurate at detecting a nuchal cord wrapped multiple times around the neck.
In no study was it possible by ultrasound to distinguish between a loose or a tight cord, although at least 3 attempted to do so. Peregrine concludes that ultrasound diagnosis of nuchal cords will only be useful if doctors are able to do so reliably and predict which of those fetuses are likely to have a problem., However, perinatologists routinely look for umbilical cord issues in monoamniotic twins. Studies have shown an improvement in outcomes where cord entanglement was prenatally identified in these cases. Ultrasound measurement of the velocity of flow in the cord may be useful in the management of twins and chronically growth-retarded fetuses. Of course this depends on the training of the sonographer. To date there are no ultrasound courses which teach the identification of nuchal cord to physicians or technicians. A recent review by Wilson of the American Academy of Ultrasonography Technicians recommends the documentation of umbilical cord issues.
Clapp, et al, attempted to find out at what rate nuchal cords come and go during pregnancy. He recruited 84 healthy, non-smoking, non-substance abusing women carrying a single fetus, with certain dates before the 20th week of gestation. They all agreed to 4 extensive ultrasounds at 24-26, 30-32, 36–38 weeks gestation and during labor and delivery. They evaluated fetal biometry, fetal tone, fetal motion including breathing movements, amniotic fluid volume, fetal flow redistribution, velocity flow profiles from the umbilical artery at the body wall and placental insertion and at the origin of fetal middle cerebral artery. Finally, color flow Doppler imaging was used to determine whether a nuchal cord was present. Clapp reports that in 60%, or 50 of the 84 fetuses studied, a nuchal cord was seen on ultrasound at one of the 4 evaluations. He found that the presence of a nuchal cord linearly increases as the pregnancy continues. Larson, et al, found this to be true. She found, of the 13,895 singleton deliveries, a nuchal cord linearly increased every week of gestation, appearing in 6% at 20 weeks to 29.0% at 42 weeks gestation.
Prognosis and treatment
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Retrospective data of over 182,000 births, with the statistical power to determine even mild associations, suggest that a single or multiple nuchal cords at the time of delivery is not associated with adverse perinatal outcomes, is associated with higher birthweights and fewer caesarean sections in births. Although some studies have found that a tight nuchal cord is associated with short term morbidity, it is unclear whether such outcomes are actually a result of the presence of the nuchal cord itself, or as a result of clamping and cutting the cord 
Management of a presenting nuchal cord should be tailored to prevent umbilical cord compression whenever possible. Techniques to preserve an intact nuchal cord depend on how tightly the cord is wrapped around the infant’s neck. If the cord is loose, it can easily be slipped over the infant’s head. The infant can be delivered normally and placed on maternal abdomen as desired. If the cord is too tight to go over the infant’s head, the provider may be able to slip it over the infant’s shoulders and deliver the body through the cord. The cord can then be unwrapped from around the baby after birth. Finally, if the cord is too tight to slip back over the shoulders, one may use the somersault maneuver to allow the body to be delivered. The birth attendant may also choose to clamp and cut the umbilical cord to allow for vaginal delivery if other methods of nuchal cord management are not feasible.
- Moldenhauer, Julie S. "Abnormal Position and Presentation of the Fetus". Merck Manual. Retrieved December 26, 2017.
- Peregrine, E.; O’Brien, P.; Jauniaux, Eric (August 2005). "Ultrasound Detection of Nuchal Cord Prior to Labor Induction and the Risk of Cesarean Section". Obstetrical & Gynecological Survey. 60 (8): 506–507. doi:10.1097/01.ogx.0000172319.27668.34. Retrieved December 26, 2017.
- Collins, Jason H. (February 2002). "Umbilical cord accidents: human studies". Seminars in Perinatology. 26 (1): 79–82. doi:10.1053/sper.2002.29860. PMID 11876571.
- Jouppila, Pentti; Kirkinen, Pertti (February 1982). "Ultrasonic diagnosis of nuchal encirclement by the umbilical cord: A case and methodological report". Journal of Clinical Ultrasound. 10 (2): 59–62. doi:10.1002/jcu.1870100205. Retrieved December 26, 2017.
- Williams, J. Whitridge (1980). Williams Obstetrics 16th Edition. Appleton & Lange, US. p. 421. ISBN 978-0838597316.
- Wilson, Bettye (March–April 2008). "Sonography of the Placenta And Umbilical Cord". Radiologic Technology. 79: 333S–345S. Retrieved December 26, 2017.
- Clapp, James F; Stepanchak, William; Hashimoto, Kazumasa; Ehrenberg, Hugh; Lopez, Beth (August 2003). "The natural history of antenatal nuchal cords". American Journal of Obstetrics & Gynecology. 189 (2): 488–493. doi:10.1067/s0002-9378(03)00371-5. PMID 14520223.
- Larson, Janet D.; Rayburn, William F.; Harlan, Victor L. (1997). "Nuchal Cord Entanglements and Gestational Age". American Journal of Perinatology. 14 (9): 555–557. doi:10.1055/s-2007-994333. Retrieved December 26, 2017.
- Mastrobattista, Joan M.; Hollier, Lisa M.; Yeomans, Edward R.; Ramin, Susan M.; Day, Mary-Clare; Sosa, Alfred; Gilstrap, Larry C. (February 2005). "Effects of nuchal cord on birthweight and immediate neonatal outcomes". American Journal of Perinatology. 22 (2): 83–85. doi:10.1055/s-2005-837737. PMID 15731986.
- Schäffer, Leonhard; Burkhardt, Tilo; Zimmermann, Roland; Kurmanavicius, Juozas (July 2005). "Nuchal cords in term and postterm deliveries—do we need to know?". Obstetrics and Gynecology. 106 (1): 23–28. doi:10.1097/01.AOG.0000165322.42051.0f. PMID 15994613.
- Sheiner, Sheiner; Abramowicz, Jacques S.; Levy, Amalia; Silberstein, Tali; Mazor, Moshe; Hershkovitz, Reli (May 2006). "Nuchal cord is not associated with adverse perinatal outcome". Archives of Gynecology and Obstetrics. 274 (2): 81–83. doi:10.1007/s00404-005-0110-2. PMID 16374604.
- Reed, Rachel; Barnes, Margaret; Allan, Jan (February 2009). "Nuchal cords: sharing the evidence with parents". British Journal of Midwifery. 17 (2): 106–109. doi:10.12968/bjom.2009.17.2.39379. Retrieved December 26, 2017.
- Reynolds, L (March 1999). "Practice tips. 'Somersault' maneuver for a tight umbilical cord". Canadian Family Physician. 45: 613. PMC . PMID 10099799.
- Jason H. Collins, MD (2013). Silent Risk: Issues about the Human Umbilical Cord. Xlibris. ISBN 978-1493114641.[self-published source]