Editing Umbilical cord

{{Short description|Conduit between embryo/fetus and the placenta}}
{{Distinguish|Umbilical cable}}
{{Infobox embryology
| Name        = Umbilical cord
| Latin       = funiculus umbilicalis
| Image       = Umbilicalcord.jpg
| Caption     = Umbilical cord of a three-minute-old baby. A medical clamp has been applied.
| Image2      =
| Caption2    =
}}

In [[Placentalia|placental]] [[mammal]]s, the '''umbilical cord''' (also called the '''navel string''',<ref>{{cite web |title=Umbilical |url=http://www.etymonline.com/index.php?frame=0&search=Umbilical+&searchmode=none |url-status=live |archive-url=https://web.archive.org/web/20160304071009/http://www.etymonline.com/index.php?frame=0&search=Umbilical+&searchmode=none |archive-date=4 March 2016 |access-date=27 March 2018 |website=Online Etymology Dictionary}}</ref> '''birth cord''' or '''''funiculus umbilicalis''''') is a conduit between the developing [[embryo]] or [[fetus]] and the [[placenta]]. During [[prenatal development]], the umbilical cord is physiologically and genetically part of the fetus and (in humans) normally contains two [[arteries]] (the [[umbilical arteries]]) and one [[vein]] (the [[umbilical vein]]), buried within [[Wharton's jelly]]. The umbilical vein supplies the fetus with [[oxygen]]ated, [[nutrient]]-rich [[blood]] from the [[placenta]].<!--
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WARNING!

On multiple occasions, people have changed this section of text to state that the umbilical arteries carry oxygenated blood to the fetus, and that the umbilical vein carries deoxygenateay. THIS IS INCORRECT. The article as it stands is correct, as the nomenclature reflects the fact that the umbilical arteries carry blood from the fetal heart, while the umbilical vein carries blood towards it.

Please pick up a copy of Gray's Anatomy before making a fool of yourself and wrecking the article in the process.
****************** -->  Conversely, the fetal heart pumps low-oxygen, nutrient-depleted blood through the umbilical arteries back to the placenta.

==Structure and development==
[[File:Cross section of the umbilical cord.jpg|thumb|upright=1.2|Cross-sectional [[micrograph]] of the human umbilical cord. [[H&E stain]]. Labelled  ''allantoic duct'' is also known as the [[urachus]].]]
[[File:8w3d with umbilical cord.gif|thumb|170px|[[Vaginal ultrasonography]] of an embryo of a [[Gestational age (obstetrics)|gestational age]] of eight weeks and three days. The embryo is surrounded by the thin membranes of the [[amniotic sac]], the umbilical cord is seen in the center, attaching the embryo to the [[placenta]].]]

The umbilical cord develops from and contains remnants of the [[yolk sac]] and [[allantois]]. It forms by the fifth week of [[human embryogenesis|development]], replacing the yolk sac as the source of nutrients for the embryo.<ref>{{cite web |url=http://www.med.yale.edu/obgyn/kliman/placenta/articles/EOR_UC/Umbilical_Cord.html |title=The Umbilical Cord<!-- Bot generated title --> |website=yale.edu |access-date=27 March 2018 |url-status=live |archive-url=https://web.archive.org/web/20130328143634/http://www.med.yale.edu/obgyn/kliman/placenta/articles/EOR_UC/Umbilical_Cord.html |archive-date=28 March 2013}}</ref> The cord is not directly connected to the mother's circulatory system, but instead joins the [[placenta]], which transfers materials to and from the maternal blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the [[crown-rump length]] of the fetus throughout [[pregnancy]]. The umbilical cord in a full term [[neonate]] is usually about {{convert|50|cm|in|abbr=off|sp=us|lk=on}} long and about {{convert|2|cm|in|sp=us}} in diameter. This diameter decreases rapidly within the placenta. The fully patent umbilical artery has two main layers: an outer layer consisting of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant [[ground substance]] staining [[Metachromasy|metachromatic]].<ref name=Meyer>{{cite journal |vauthors=Meyer WW, Rumpelt HJ, Yao AC, Lind J |title=Structure and closure mechanism of the human umbilical artery |journal=Eur. J. Pediatr. |volume=128 |issue=4 |pages=247–59 |date=July 1978 |pmid=668732 |doi= 10.1007/BF00445610|s2cid=37516644 }}</ref> The smooth muscle cells of the layer are rather poorly differentiated, contain only a few tiny [[myofilament]]s and are thereby unlikely to contribute actively to the process of post-natal closure.<ref name=Meyer/>

The umbilical cord can be detected by ultrasound by six weeks of gestation and well-visualized by eight to nine weeks of gestation.<ref>{{Cite journal |last1=Moshiri |first1=Mariam |last2=Zaidi |first2=Sadaf F. |last3=Robinson |first3=Tracy J. |last4=Bhargava |first4=Puneet |last5=Siebert |first5=Joseph R. |last6=Dubinsky |first6=Theodore J. |last7=Katz |first7=Douglas S. |date=January 2014 |title=Comprehensive Imaging Review of Abnormalities of the Umbilical Cord |url=http://pubs.rsna.org/doi/10.1148/rg.341125127 |journal=RadioGraphics |language=en |volume=34 |issue=1 |pages=179–196 |doi=10.1148/rg.341125127 |pmid=24428290 |issn=0271-5333|url-access=subscription }}</ref>

The umbilical [[cord lining]] is a good source of mesenchymal and epithelial stem cells. Umbilical cord [[mesenchymal stem cell]]s (UC-MSC) have been used clinically to treat osteoarthritis, autoimmune diseases, and multiple other conditions. Their advantages include a better harvesting, and multiplication, and immunosuppressive properties that define their potential for use in transplantations. Their use would also overcome the ethical objections raised by the use of [[embryonic stem cell]]s.<ref name="Saleh">{{cite journal |last1=Saleh |first1=R |last2=Reza |first2=HM |title=Short review on human umbilical cord lining epithelial cells and their potential clinical applications. |journal=Stem Cell Research & Therapy |date=10 October 2017 |volume=8 |issue=1 |pages=222 |doi=10.1186/s13287-017-0679-y |pmid=29017529 |pmc=5634865 |doi-access=free }}</ref>

The umbilical cord contains [[Wharton's jelly]], a gelatinous substance made largely from [[mucopolysaccharides]] that protects the blood vessels inside. It contains one vein, which carries oxygenated, nutrient-rich blood to the fetus, <!--
****************** 
WARNING!

On multiple occasions, people have changed this section of text to state that the umbilical arteries carry oxygenated blood to the fetus, and that the umbilical vein carries deoxygenated blood away. THIS IS INCORRECT. The article as it stands is correct, as the nomenclature reflects the fact that the umbilical arteries carry blood from the fetal heart, while the umbilical vein carries blood towards it.

Please pick up a copy of Gray's Anatomy before making a fool of yourself and wrecking the article in the process. Who is the person wrecking the article by not READING that the umbilical cord has TWO veins and ONE artery?  The Umbilical cord does NOT have 2 veins and 1 artery, but the opposite.<ref>http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/SymptomsDiagnosisofCongenitalHeartDefects/Fetal-Circulation_UCM_315674_Article.jsp#.WHGPgPkrLIU {{Bare URL inline|date=May 2022}}</ref>
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--> and two arteries that carry deoxygenated, nutrient-depleted blood away.<ref>{{cite web |url=http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/SymptomsDiagnosisofCongenitalHeartDefects/Fetal-Circulation_UCM_315674_Article.jsp#.WHGPgPkrLIU|title=Fetal Circulation |website=www.heart.org |access-date=27 March 2018 |url-status=live |archive-url=https://web.archive.org/web/20171222042027/http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/SymptomsDiagnosisofCongenitalHeartDefects/Fetal-Circulation_UCM_315674_Article.jsp#.WHGPgPkrLIU |archive-date=22 December 2017}}</ref> Occasionally, only two vessels (one vein and one artery) are present in the umbilical cord. This is sometimes related to fetal abnormalities, but it may also occur without accompanying problems.

It is unusual for a vein to carry oxygenated blood and for arteries to carry deoxygenated blood (the only other examples being the [[pulmonary veins]] and [[pulmonary arteries|arteries]], connecting the lungs to the heart). However, this naming convention reflects the fact that the umbilical vein carries blood towards the fetus' heart, while the umbilical arteries carry blood away.

The blood flow through the umbilical cord is approximately 35 ml / min at 20 weeks, and 240 ml / min at 40 [[Gestational age (obstetrics)|weeks of gestation]].<ref name=kiserud2004>{{Cite journal |last1 = Kiserud |first1 = T. |last2 = Acharya |first2 = G. |doi = 10.1002/pd.1062 |title = The fetal circulation |journal = Prenatal Diagnosis |volume = 24 |issue = 13 |pages = 1049–1059 |year = 2004 |pmid = 15614842 |s2cid = 25040285 }}</ref> Adapted to the weight of the fetus, this corresponds to 115 ml / min / kg at 20 weeks and 64 ml / min / kg at 40 weeks.<ref name=kiserud2004/>

For [[Anatomical terms of location|terms of location]], the ''proximal'' part of an umbilical cord refers to the segment closest to the embryo or fetus in embryology and fetal medicine, and closest to the placenta in placental pathology, and opposite for the ''distal'' part, respectively.<ref>{{cite web |url=https://patholines.org/Placenta |title=Placenta |website=patholines.org |access-date=2023-04-07 |author=Mikael Häggström, MD |date=2020-08-27}}</ref>

==Function==
===Connection to fetal circulatory system===
The umbilical cord enters the fetus via the [[Human abdomen|abdomen]], at the point which (after separation) will become the [[navel|umbilicus]] (belly button or navel). Within the fetus, the umbilical vein continues towards the [[Transverse fissure of liver|transverse fissure]] of the [[liver]], where it splits into two. One of these branches joins with the [[hepatic portal vein]] (connecting to its left branch), which carries blood into the liver. The second branch (known as the [[ductus venosus]]) bypasses the liver and flows into the [[inferior vena cava]], which carries blood towards the heart. The two umbilical arteries branch from the [[internal iliac arteries]] and pass on either side of the [[urinary bladder]] into the umbilical cord, completing the circuit back to the placenta.<ref>{{cite web|url=http://education.yahoo.com/reference/gray/subjects/subject/139 |title=Peculiarities in the Vascular System in the Fetus – Gray's Anatomy of the Human Body – Yahoo! Education |url-status=dead |archive-url=https://web.archive.org/web/20120123194946/http://education.yahoo.com/reference/gray/subjects/subject/139 |archive-date=January 23, 2012 }}</ref>

===Changes after birth===
After birth, the umbilical cord stump will dry up and drop away by the time the baby is three weeks old.<ref name=":0">{{Cite web |title=Umbilical cord care: Do's and don'ts for parents |url=https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/umbilical-cord/art-20048250 |access-date=2022-06-12 |website=Mayo Clinic |language=en}}</ref> If the stump still has not separated after three weeks, it might be a sign of an underlying problem, such as an infection or immune system disorder.<ref name=":0" />

In absence of external interventions, the umbilical cord [[Vascular occlusion|occludes]] physiologically shortly after birth, explained both by a swelling and collapse of [[Wharton's jelly]] in response to a reduction in temperature and by [[vasoconstriction]] of the blood vessels by smooth muscle contraction. In effect, a natural clamp is created, halting the flow of blood. In air at 18&nbsp;°C, this physiological clamping will take three minutes or less.<ref>{{cite journal|last=Cohain|first=J. S.|title=A Proposed Protocol for Third Stage Management – Judy's 3,4,5,10 minute method|journal=Birth|year=2010|volume=37|issue=1|pages=84–85|doi=10.1111/j.1523-536x.2009.00385_2.x|pmid=20402731}}</ref> In [[water birth]], where the water temperature is close to body temperature, normal pulsation can be five minutes and longer.<!--http://www.webmedcentral.com/article_view/2993-->

Closure of the umbilical artery by vasoconstriction consists of multiple constrictions which increase in number and degree with time. There are segments of dilations with trapped uncoagulated blood between the constrictions before complete occlusion.<ref>{{cite journal |vauthors=Yao AC, Lind J, Lu T |title=Closure of the human umbilical artery: a physiological demonstration of Burton's theory |journal=Eur. J. Obstet. Gynecol. Reprod. Biol. |volume=7 |issue=6 |pages=365–8 |year=1977 |pmid=264063 |doi= 10.1016/0028-2243(77)90064-8}}</ref> Both the partial constrictions and the ultimate closure are mainly produced by muscle cells of the outer circular layer.<ref name=Meyer/> In contrast, the inner layer seems to serve mainly as a plastic tissue which can easily be shifted in an [[Anatomical directions|axial]] direction and then folded into the narrowing lumen to complete the closure.<ref name=Meyer/> The vasoconstrictive occlusion appears to be mainly mediated by [[serotonin]]<ref name=Quan/><ref name=white>{{cite journal |author=White RP |title=Pharmacodynamic study of maturation and closure of human umbilical arteries |journal=Am. J. Obstet. Gynecol. |volume=160 |issue=1 |pages=229–37 |date=January 1989 |pmid=2912087 |doi= 10.1016/0002-9378(89)90127-0}}</ref> and [[thromboxane A2|thromboxane A<sub>2</sub>]].<ref name=Quan>{{cite journal |vauthors=Quan A, Leung SW, Lao TT, Man RY |title=5-hydroxytryptamine and thromboxane A2 as physiologic mediators of human umbilical artery closure |journal=J. Soc. Gynecol. Investig. |volume=10 |issue=8 |pages=490–5 |date=December 2003 |pmid=14662162 |doi= 10.1016/S1071-5576(03)00149-7}}</ref> The artery in cords of preterm infants contracts more to [[angiotensin II]] and [[arachidonic acid]] and is more sensitive to [[oxytocin]] than in term ones.<ref name=white/> In contrast to the contribution of Wharton's jelly, cooling causes only temporary vasoconstriction.<ref name=white/>

Within the child, the umbilical vein and ductus venosus close up, and degenerate into fibrous remnants known as the [[round ligament of the liver]] and the [[ligamentum venosum]] respectively. Part of each umbilical artery closes up (degenerating into what are known as the [[medial umbilical ligament]]s), while the remaining sections are retained as part of the circulatory system.

==Clinical significance==
===Problems and abnormalities===
{{anchor|knot}}[[File:Knotted cord.jpg|thumb|A ''knotted cord'' on a newborn baby]]

A number of abnormalities can affect the umbilical cord, which can cause problems that affect both mother and child:<ref name="urlUmbilical Cord Complications: eMedicine Obstetrics and Gynecology">{{cite web|url=http://emedicine.medscape.com/article/262470-overview|title=Umbilical Cord Complications: eMedicine Obstetrics and Gynecology|access-date=2010-01-24|url-status=live|archive-url=https://web.archive.org/web/20100129065851/http://emedicine.medscape.com/article/262470-overview|archive-date=2010-01-29}}</ref>
* [[Umbilical cord compression]] can result from, for example, entanglement of the cord,<ref name=icd10/> a knot in the cord,<ref name=icd10/> or a [[nuchal cord]],<ref name=icd10>[http://apps.who.int/classifications/icd10/browse/2010/en#/P02.5 P02.5 Fetus and newborn affected by other compression of umbilical cord] {{webarchive|url=https://web.archive.org/web/20141102133725/http://apps.who.int/classifications/icd10/browse/2010/en |date=2014-11-02 }} in [[ICD-10]], the International Statistical Classification of Diseases</ref> (which is the wrapping of the umbilical cord around the fetal neck)<ref name="urlFetus or Newborn Problems: Labor and Delivery Complications: Merck Manual Home Edition">{{cite web|url=http://www.merck.com/mmhe/sec22/ch261/ch261c.html#sec22-ch261-ch261c-1292a|title=Fetus or Newborn Problems: Labor and Delivery Complications: Merck Manual Home Edition|access-date=2010-03-27|url-status=live|archive-url=https://web.archive.org/web/20100328183737/http://www.merck.com/mmhe/sec22/ch261/ch261c.html#sec22-ch261-ch261c-1292a|archive-date=2010-03-28}}</ref> but these conditions do not always cause obstruction of fetal circulation.
* [[Velamentous cord insertion]]
* [[Single umbilical artery]]
* [[Umbilical cord prolapse]]
* [[Vasa praevia]]

===Clamping and cutting===
[[File:Caesarean section operation -cutting the umbilical cord-8Feb2011.jpg|thumb|The umbilical cord is about to be cut with scissors via caesarean section]]
[[File:Umbical cord clamp 2005.jpg|thumb|right|Umbilical cord clamp]]
[[File:Human-Male-Newborn-Infant-Baby.jpg|thumb|right|A day-old baby with the cord stump still attached.]]
[[File:Detached Umbilical Cord.jpg|thumb|right|A {{convert|7|cm|in|abbr=on}} long detached umbilical cord.]]

The cord can be clamped at different times; however, delaying the clamping of the umbilical cord until at least one minute after birth improves outcomes as long as there is the ability to treat the small risk of [[jaundice]] if it occurs.<ref>{{cite journal|last=McDonald|first=SJ|author2=Middleton, P |author3=Dowswell, T |author4= Morris, PS |title=Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes.|journal=The Cochrane Database of Systematic Reviews|date=Jul 11, 2013|volume=7|issue=7|pages=CD004074|pmid=23843134|pmc=6544813|doi=10.1002/14651858.CD004074.pub3}}</ref> Clamping is followed by cutting of the cord, which is painless due to the absence of [[nerve]]s. The cord is extremely tough, like thick [[sinew]], and so cutting it requires a suitably sharp instrument. While umbilical severance may be delayed until after the cord has stopped pulsing (one to three minutes after birth), there is ordinarily no significant loss of either venous or arterial blood while cutting the cord. Current evidence neither supports, nor refutes, delayed cutting of the cord, according to the [[American Congress of Obstetricians and Gynecologists]] (ACOG) guidelines.

There are umbilical cord clamps which incorporate a knife. These clamps are safer and faster, allowing one to first apply the cord clamp and then cut the umbilical cord. After the cord is clamped and cut, the newborn wears a plastic clip on the navel area until the compressed region of the cord has dried and sealed sufficiently.

The length of umbilical left attached to the newborn varies by practice; in most hospital settings the length of cord left attached after clamping and cutting is minimal. In the United States, however, where the birth occurred outside of the hospital and an [[emergency medical technician]] (EMT) clamps and cuts the cord, a longer segment up to {{convert|18|cm|in|abbr=on|0}} in length<ref>{{cite web | url=http://danedocs.countyofdane.com/webdocs/PDF/ems/medical/emt_protocols.pdf | title=EMT-BASIC \ EMT BASIC INTERMEDIATE TECHNICIAN PROTOCOLS | publisher=Dane County Emergency Medical Services | date=May 2007 | access-date=December 17, 2011 | author=Stiegler, Paul M., M.D. | url-status=live | archive-url=https://web.archive.org/web/20120406130532/http://danedocs.countyofdane.com/webdocs/PDF/ems/medical/emt_protocols.pdf | archive-date=April 6, 2012 }}</ref><ref>{{cite web | url=http://www.nursingceu.com/courses/340/index_ems.html | title=EMT-B: Obstetrics, Infants and Children | publisher=Wild Iris Medical Education | access-date=December 17, 2011 | author=Meersman, Jack | url-status=live | archive-url=https://web.archive.org/web/20120120231740/http://www.nursingceu.com/courses/340/index_ems.html | archive-date=January 20, 2012 }}</ref> is left attached to the newborn.

The remaining umbilical stub remains for up to ten days as it dries and then falls off.

====Early versus delayed clamping====
A [[Cochrane review]] in 2013 came to the conclusion that delayed cord clamping (between one and three minutes after birth) is "likely to be beneficial as long as access to treatment for jaundice requiring phototherapy is available".<ref name=McDonald2013>{{Cite journal | last1 = McDonald | first1 = S. J. | last2 = Middleton | first2 = P. | last3 = Dowswell | first3 = T. | last4 = Morris | first4 = P. S. | editor1-last = McDonald | editor1-first = Susan J | title = Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes | doi = 10.1002/14651858.CD004074.pub3 |journal=The Cochrane Database of Systematic Reviews| year = 2013 | pmid =  23843134| pmc =6544813 | volume=7 | issue = 7 | pages=CD004074}}</ref> In this review delayed clamping, as contrasted to early, resulted in no difference in risk of severe maternal [[postpartum hemorrhage]] or neonatal mortality, and a low [[Apgar score]]. On the other hand, delayed clamping resulted in an increased birth weight of on average about 100 g, and an increased [[hemoglobin]] concentration of on average 1.5 g/dL with half the risk of being iron deficient at three and six months, but an increased risk of jaundice requiring [[Neonatal jaundice#Phototherapy|phototherapy]].<ref name=McDonald2013/>

In 2012, the American College of Obstetricians and Gynecologists officially endorsed delaying clamping of the umbilical cord for 30–60 seconds with the newborn held below the level of the placenta in all cases of preterm delivery based largely on evidence that it reduces the risk of intraventricular hemorrhage in these children by 50%.<ref name=ACOG_2012>{{cite journal|last=Committee on Obstetric Practice, American College of Obstetricians and|first=Gynecologists|title=Committee Opinion No.543: Timing of umbilical cord clamping after birth.|journal=Obstetrics and Gynecology|date=December 2012|volume=120|issue=6|pages=1522–6|pmid=23168790|doi=10.1097/01.aog.0000423817.47165.48}}</ref>{{obsolete source|date=January 2017}} In the same committee statement, ACOG also recognize several other likely benefits for preterm infants, including "improved transitional circulation, better establishment of red blood cell volume, and decreased need for blood transfusion". In January 2017, a revised Committee Opinion extended the recommendation to term infants, citing data that term infants benefit from increased hemoglobin levels in the newborn period and improved iron stores in the first months of life, which may result in improved developmental outcomes. ACOG recognized a small increase in the incidence of jaundice in term infants with delayed cord clamping, and recommended policies be in place to monitor for and treat neonatal jaundice. ACOG also noted that delayed cord clamping is not associated with increased risk of postpartum hemorrhage.<ref>{{Cite journal|date=2017-01-01|title=Committee Opinion No. 684|journal=Obstetrics & Gynecology|language=en|volume=129|issue=1|pages=e5–e10|doi=10.1097/aog.0000000000001860|pmid=28002310|issn=1873-233X|author1=Committee on Obstetric Practice}}</ref>

Several studies have shown benefits of delayed cord clamping: A meta-analysis<ref name="hutton2007" /> showed that delaying clamping of the umbilical cord in full-term neonates for a minimum of two minutes following birth is beneficial to the newborn in giving improved [[hematocrit]], iron status as measured by [[ferritin]] concentration and stored iron, as well as a reduction in the risk of anemia ([[relative risk]], 0.53; 95% CI, 0.40–0.70).<ref name="hutton2007" /> A decrease was also found in a study from 2008.<ref name="newborn_neonatal_116-117">Examination of the Newborn & Neonatal Health: A Multidimensional Approach, p. 116-117</ref> Although there is higher hemoglobin level at 2 months, this effect did not persist beyond 6 months of age.<ref name="cochrane2008">"Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes." ''Cochrane Database Syst Rev''. 2008; (2):CD004074</ref> Not clamping the cord for three minutes following the birth of a baby improved outcomes at four years of age.<ref>{{cite journal |last1=Andersson |first1=O |last2=Lindquist |first2=B |last3=Lindgren |first3=M |last4=Stjernqvist |first4=K |last5=Domellöf |first5=M|last6=Hellström-Westas|first6=L|title=Effect of Delayed Cord Clamping on Neurodevelopment at 4 Years of Age: A Randomized Clinical Trial.|journal=JAMA Pediatrics|date=1 July 2015 |volume=169 |issue=7 |pages=631–8 |pmid=26010418 |doi=10.1001/jamapediatrics.2015.0358 |doi-access=free}}</ref> A delay of three minutes or more in umbilical cord clamping after birth reduce the prevalence of anemia in infants.<ref>{{cite web|url=https://medicalxpress.com/news/2017-01-umbilical-cord-clamping-infant-anemia.html |title=Can delayed umbilical cord clamping reduce infant anemia at age 8, 12 months?|website=medicalxpress.com|access-date=27 March 2018|url-status=live|archive-url=https://web.archive.org/web/20180225144902/https://medicalxpress.com/news/2017-01-umbilical-cord-clamping-infant-anemia.html |archive-date=25 February 2018}}</ref>

Negative effects of delayed cord clamping include an increased risk of [[polycythemia]]. Still, this condition appeared to be benign in studies.<ref name=hutton2007>{{cite journal |vauthors=Hutton EK, Hassan ES |title=Late vs early clamping of the umbilical cord in full-term neonates: systematic review and meta-analysis of controlled trials |journal=JAMA |volume=297 |issue=11 |pages=1241–52 |date=March 2007 |pmid=17374818 |doi=10.1001/jama.297.11.1241 }}</ref> Infants whose cord clamping occurred later than 60 seconds after birth had a higher rate of [[neonatal jaundice]] requiring [[phototherapy]].<ref name=cochrane2008 />

Delayed clamping is not recommended as a response to cases where the newborn is not breathing well and needs resuscitation. Rather, the recommendation is instead to immediately clamp and cut the cord and perform [[cardiopulmonary resuscitation]].<ref>[http://www.brooksidepress.org/Products/Military_OBGYN/Textbook/LaborandDelivery/delivery_of_the_baby.htm Military Obstetrics & Gynecology – Delivery of the Baby] {{webarchive|url=https://web.archive.org/web/20100123154710/http://www.brooksidepress.org/Products/Military_OBGYN/Textbook/LaborandDelivery/delivery_of_the_baby.htm |date=2010-01-23 }} The Brookside Associates Medical Education Division. Retrieved Jan 10, 2009</ref> The umbilical cord pulsating is not a guarantee that the baby is receiving enough oxygen.<ref>[http://www.waterbirth.org/mc/page.do?sitePageId=38564 Waterbirth International – Waterbirth FAQ] {{Webarchive|url=https://web.archive.org/web/20110318005355/http://www.waterbirth.org/mc/page.do?sitePageId=38564 |date=2011-03-18 }} Retrieved Jan 10, 2009</ref>

====Umbilical nonseverance====
Some parents choose to omit cord severance entirely, a practice called "[[lotus birth]]" or umbilical nonseverance. The entire intact umbilical cord is allowed to dry and separates on its own (typically on the 3rd day after birth), falling off and leaving a healed umbilicus.<ref>{{cite journal |last1=Crowther |first1=S |author-link=Susan Crowther |year=2006 |title=Lotus birth: leaving the cord alone |journal=The Practising Midwife |volume=9 |issue=6 |pages=12–14 |pmid=16830839}}</ref> The [[Royal College of Obstetricians and Gynaecologists]] has warned about the risks of infection as the decomposing placenta tissue becomes a nest for infectious bacteria such as [[Staphylococcus]].<ref name=RCOG>{{Cite news|date=2008-12-01|url=https://www.rcog.org.uk/en/news/rcog-statement-on-umbilical-non-severance-or-lotus-birth|title=RCOG statement on umbilical non-severance or "lotus birth"|website=[[Royal College of Obstetricians and Gynaecologists]]|language=en-US|archive-url=https://web.archive.org/web/20170322221453/https://www.rcog.org.uk/en/news/rcog-statement-on-umbilical-non-severance-or-lotus-birth|archive-date=2017-03-22|access-date=2020-02-06}}</ref> In one such case, a 20-hour old baby whose parents chose UCNS was brought to the hospital in an agonal state, was diagnosed with [[sepsis]] and required an antibiotic treatment for six weeks.<ref>{{Cite journal|title=Umbilical Cord Nonseverance and Adverse Neonatal Outcomes |journal=Clinical Pediatrics|volume=58|issue=2|pages=238–240|language=en|doi=10.1177/0009922818805243|pmid=30280596|year = 2019|last1 = Ittleman|first1 = Benjamin R.|last2=German|first2=Kendell R.|last3=Scott|first3=Emily|last4=Walker|first4=Valencia|last5=Flaherman|first5=Valerie J.|last6=Szabo|first6=Joanne|last7=Beavers|first7=Jessica B.|s2cid=52912265}}</ref><ref>{{Cite web|url=http://www.skepticalob.com/2018/12/lotus-birth-leaves-a-newborn-critically-ill-with-a-heart-infection.html|title=Lotus birth leaves a newborn critically ill with a heart infection|last=MD|first=Amy Tuteur|date=2018-12-19|website=The Skeptical OB|access-date=2018-12-20}}</ref>

====Umbilical cord catheterization====
As the umbilical vein is directly connected to the central circulation, it can be used as a route for placement of a venous catheter for infusion and medication. The umbilical vein catheter is a reliable alternative to percutaneous peripheral or central venous catheters or intraosseous canulas and may be employed in resuscitation or intensive care of the newborn.

====Blood sampling====
From 24 to 34 weeks of gestation, when the fetus is typically viable, blood can be taken from the cord in order to test for abnormalities (particularly for [[hereditary]] conditions). This diagnostic [[genetic testing|genetic test]] procedure is known as [[percutaneous umbilical cord blood sampling]].<ref>{{cite web |url=http://library.med.utah.edu/kw/human_reprod/lectures/clinical_genetics/ |title=Human Reproduction, Lectures: Clinical Genetics |access-date=2010-02-11}}</ref>

===Storage of cord blood===
{{main|Cord blood}}

The blood within the umbilical cord, known as [[cord blood]], is a rich and readily available source of primitive, [[Cellular differentiation|undifferentiated]] [[stem cell]]s (of type [[CD34]]-positive and [[CD38]]-negative). These cord blood cells can be used for [[bone marrow transplant]].

Some parents choose to have this blood diverted from the baby's umbilical blood transfer through early cord clamping and cutting, to freeze for long-term storage at a [[cord blood bank]] should the child ever require the cord blood stem cells (for example, to replace [[bone marrow]] destroyed when treating [[leukemia]]). This practice is controversial, with critics asserting that early cord blood withdrawal at the time of birth actually increases the likelihood of childhood disease, due to the high volume of blood taken (an average of 108ml) in relation to the baby's total supply (typically 300ml).<ref name="newborn_neonatal_116-117" />  The [[Royal College of Obstetricians and Gynaecologists]] stated in 2006 that "there is still insufficient evidence to recommend directed commercial cord blood collection and stem-cell storage in low-risk families".<ref>{{Cite web|first=|date=2006|title=Umbilical Cord Blood Banking|url=https://www.rcog.org.uk/globalassets/documents/guidelines/scientific-impact-papers/sip_2.pdf|access-date=2021-07-01|publisher=Royal College of Obstetricians and Gynaecologists|type=Scientific Impact Paper 8}}</ref>

The [[American Academy of Pediatrics]] has stated that cord blood banking for self-use should be discouraged (as most conditions requiring the use of stem cells will already exist in the cord blood), while banking for general use should be encouraged.<ref name="aap_statement">{{cite web |title=Cord Blood Banking for Potential Future Transplantation |url=http://aappolicy.aappublications.org/cgi/content/full/pediatrics;119/1/165 |author=American Academy of Pediatrics |url-status=live |archive-url=https://web.archive.org/web/20071013194154/http://aappolicy.aappublications.org/cgi/content/full/pediatrics;119/1/165 |archive-date=2007-10-13 |author-link=American Academy of Pediatrics }}</ref>  In the future, cord blood-derived embryonic-like stem cells (CBEs) may be banked and matched with other patients, much like blood and transplanted tissues. The use of CBEs could potentially eliminate the ethical difficulties associated with [[embryonic stem cells]] (ESCs).<ref>[https://www.newscientist.com/article.ns?id=dn7864 "Cord blood yields 'ethical' embryonic stem cells."] {{webarchive|url=https://web.archive.org/web/20081010082806/http://www.newscientist.com/article.ns?id=dn7864 |date=2008-10-10 }}, Coghlin A. ''[[New Scientist]]'', August 18, 2005. Accessed June 25, 2007.</ref>

While the American Academy of Pediatrics discourages private banking except in the case of existing medical need, it also says that information about the potential benefits and limitations of cord blood banking and transplantation should be provided so that parents can make an informed decision.

In the United States, cord blood education has been supported by legislators at the federal and state levels. In 2005, the National Academy of Sciences published an [https://web.archive.org/web/20091123092544/http://www.iom.edu/en/Activities/Research/CordBloodBank.aspx Institute of Medicine (IoM) report] which recommended that expectant parents be given a balanced perspective on their options for cord blood banking. In response to their constituents, state legislators across the country are introducing legislation intended to help inform physicians and expectant parents on the options for donating, discarding or banking lifesaving newborn stem cells. Currently 17 states, representing two-thirds of U.S. births, have enacted legislation recommended by the IoM guidelines.

The use of cord blood stem cells in treating conditions such as brain injury<ref>[http://clinicaltrials.gov/ct2/show/NCT00593242?term=NCT00593242&rank=1 Cord Blood for Neonatal Hypoxic-Ischemic Encephalopathy] {{webarchive|url=http://archive.wikiwix.com/cache/20110812025757/http://clinicaltrials.gov/ct2/show/NCT00593242?term=NCT00593242&rank=1 |date=2011-08-12 }}, Autologous Cord Blood Cells for Hypoxic Ischemic Encephalopathy Study 1. Phase I Study of Feasibility and Safety</ref>  and Type 1 Diabetes<ref>{{cite journal
| doi     = 10.1016/j.exphem.2008.01.009
| author  = Haller MJ
| last2   = Viener
| first2  = HL
| last3   = Wasserfall
| first3  = C
| last4   = Brusko
| first4  = T
| last5   = Atkinson
| first5  = MA
| last6   = Schatz
| first6  = DA
| title   = Autologous Umbilical Cord Blood Infusion for Type 1 Diabetes
| journal = Exp. Hematol.
| volume  = 36
| issue   = 6
| pages   = 710–715
| year    = 2008
| pmid    = 18358588
| pmc     = 2444031
|display-authors=etal}}</ref>  is already being studied in humans, and earlier stage research is being conducted for treatments of stroke,<ref>{{cite journal
| doi     = 10.1016/j.expneurol.2006.03.017
 |vauthors=Vendrame M, etal | title   = Cord blood rescues stroke-induced changes in splenocyte phenotype and function
| journal = Exp. Neurol.
| volume  = 199
| issue   = 1
| pages   = 191–200
| year    = 2006
| pmid    = 16713598
|s2cid=29804539 }}</ref><ref>{{cite journal
| doi     = 10.1089/scd.2005.14.595
 |vauthors=Vendrame M, etal | title   = Anti-inflammatory effects of human cord blood cells in a rat model of stroke
| journal = Stem Cells Dev.
| volume  = 14
| issue   = 5
| pages   = 595–604
| year    = 2005
| pmid    = 16305344
}}</ref> and hearing loss.<ref>{{cite journal
| doi     = 10.3727/096368908786092685
 |vauthors=Revoltella RP, etal | title   = Cochlear repair by transplantation of human cord blood CD133+ cells to nod-scid mice made deaf with kanamycin and noise
| journal = Cell Transplant.
| volume  = 17
| issue   = 6
| pages   = 665–678
| year    = 2008
| pmid    = 18819255
| doi-access=
| hdl= 11577/139892
|s2cid=27705881 | hdl-access= free
}}</ref>

Cord blood stored with private banks is typically reserved for use of the donor child only. In contrast, cord blood stored in public banks is accessible to anyone with a closely matching tissue type and demonstrated need.<ref>{{Cite news|last=Najjar|first=Dana|date=2020-12-18|title=Should You Bank Your Baby's Cord Blood?|language=en-US|work=The New York Times|url=https://www.nytimes.com/2020/12/18/parenting/pregnancy/cord-blood-banking.html|access-date=2021-07-01|issn=0362-4331}}</ref> The use of cord blood from public banks is increasing. Currently it is used in place of a bone marrow transplant in the treatment of blood disorders such as leukemia, with donations released for transplant through one registry, Netcord.org,<ref>{{cite web |url=http://netcord.affiniscape.com/associations/8311/files/Press%20release%20final%20-%20WBMT.pdf |title=All-In-One Association Member Management System &#124; YourMembership |access-date=2013-04-13 |url-status=live |archive-url=https://web.archive.org/web/20131102154654/http://netcord.affiniscape.com/associations/8311/files/Press%20release%20final%20-%20WBMT.pdf |archive-date=2013-11-02 }}</ref> passing 1,000,000 as of January 2013. Cord blood is used when the patient cannot find a matching bone marrow donor; this "extension" of the donor pool has driven the expansion of public banks.

==The umbilical cord in other animals==
The umbilical cord in some mammals, including cattle and sheep, contains two distinct umbilical veins. There is only one umbilical vein in the human umbilical cord.<ref name="meat_hygiene">''Meat Hygiene''. J. F. Gracey, D. S. Collins, Robert J. Huey. p. 32.</ref>

In some animals, the mother will gnaw through the cord, thus separating the placenta from the offspring. The cord along with the placenta is often eaten by the mother, to provide nourishment and to dispose of tissues that would otherwise attract scavengers or predators.{{citation needed|date=March 2017}} In [[Common chimpanzee|chimpanzee]]s, the mother leaves the cord in place and nurses her young with the cord and placenta attached until the cord dries out and separates naturally, within a day of birth, at which time the cord is discarded.  (This was first documented by zoologists in the wild in 1974.<ref>See ''In the Shadow of Man'', by Jane Goodall.</ref>)

Some species of [[shark]]—[[hammerhead shark|hammerheads]], [[requiem shark|requiems]] and [[smooth-hound]]s—are [[Viviparity|viviparous]] and have an umbilical cord attached to their placenta.<ref>{{cite web|url=http://www.fao.org/docrep/006/y5261e/y5261e08.htm|title=Sharks (Chondrichthyes)|publisher=FAO|access-date=2009-09-14|url-status=live|archive-url=https://web.archive.org/web/20080802000017/http://www.fao.org/docrep/006/y5261e/y5261e08.htm|archive-date=2008-08-02}}</ref>

==Other uses for the term "umbilical cord"==
The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the hose connecting [[Surface-supplied diving|surface-supplied divers]] to their surface supply of air and/or heating, or [[space-suit]]ed [[astronaut]]s to their spacecraft. Engineers sometimes use the term to describe a complex or critical cable connecting a component, especially when composed of bundles of conductors of different colors, thickness and types, terminating in a single multi-contact disconnect.

==Cancer-causing toxicants in human umbilical cords==
In multiple American and international studies, [[carcinogen|cancer-causing]] chemicals have been found in the blood of umbilical cords. These originate from certain plastics, computer circuit boards, fumes and synthetic fragrances among others. Over 300 [[Chemical substance|chemical]] [[Toxicity#Types|toxicants]] have been found, including [[bisphenol A]] (BPA), [[tetrabromobisphenol A]] (TBBPA), [[Teflon]]-related [[perfluorooctanoic acid]], [[galaxolide]] and [[synthetic musk]]s among others.<ref>{{cite journal|title=Perfluorinated Compounds in Umbilical Cord Blood and Adverse Birth Outcomes|first1=Mei-Huei|last1=Chen|first2=Eun-Hee|last2=Ha|first3=Ting-Wen|last3=Wen|first4=Yi-Ning|last4=Su|first5=Guang-Wen|last5=Lien|first6=Chia-Yang|last6=Chen|first7=Pau-Chung|last7=Chen|first8=Wu-Shiun|last8=Hsieh|date=3 August 2012|journal=PLOS ONE|volume=7|issue=8|pages=e42474|doi=10.1371/journal.pone.0042474|pmid=22879996|pmc=3411780|bibcode=2012PLoSO...742474C|doi-access=free}}</ref> The studies in America showed higher levels in [[African Americans]], [[Hispanic Americans]] and [[Asian Americans]] due, it is thought, to living in areas of higher pollution.<ref>{{cite web |url=http://www.scientificamerican.com/article.cfm?id=chemicals-umbilical-cord-blood |title=Why Are Trace Chemicals Showing up in Umbilical Cord Blood? |website=[[Scientific American]] |access-date=2012-09-01 |url-status=live |archive-url=https://web.archive.org/web/20120902091812/http://www.scientificamerican.com/article.cfm?id=chemicals-umbilical-cord-blood |archive-date=2012-09-02 }}</ref>

==Additional images==
<gallery>
File:Gray34.png|Sectional plan of the gravid uterus in the third and fourth month.
File:Gray38.png|Fetus in utero, between fifth and sixth months.
File:Newborn umbilical suction.jpg|A newborn at 45 seconds, with umbilical cord clamped.
File:Slide2BLA.JPG|Umbilic. Deep dissection. Serial cross section.
File:Umbcord.jpg|dried umbilical cord stump.
</gallery>

==See also==
* [[Navel]]
* [[Umbilical line]]

==References==
{{reflist|30em}}
* {{Cite journal |author=Marianne Messerli |display-authors=etal |date=December 2013 |title=Stem Cells from Umbilical Cord Wharton's Jelly from Preterm Birth Have Neuroglial Differentiation Potential |journal=[[Reproductive Sciences]] |volume=20 |issue=12 |pages=1455–1464 |doi=10.1177/1933719113488443 |pmid=23670950 |pmc=3817666 }}

== External links ==
* {{Commons-inline}}

{{Extraembryonic and fetal membranes}}
{{Authority control}}

[[Category:Childbirth]]
[[Category:Cloning]]
[[Category:Embryology]]
[[Category:Stem cells]]
[[Category:Vertebrate developmental biology]]
[[Category:Navel]]