You are in: eMedicine Specialties > Obstetrics and Gynecology > Obstetrical Complications Umbilical Cord ComplicationsArticle Last Updated: Aug 15, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Marie Helen Beall, MD, Vice Chair, Clinical Professor, Department of Obstetrics and Gynecology, Geffen School of Medicine, University of California at Los Angeles-Harbor Medical Center Marie Helen Beall is a member of the following medical societies: American College of Medical Genetics, American College of Obstetricians and Gynecologists, and American Society of Human Genetics Coauthor(s): Michael G Ross, MD, MPH, Professor of Obstetrics/Gynecology and Public Health, David Geffen School of Medicine at UCLA, UCLA School of Public Health; Chair, Department of Obstetrics/Gynecology, Harbor-UCLA Medical Center Editors: Ronald Levine, MD, Director, Section of Gynecologic Endoscopy, Professor, Department of Obstetrics and Gynecology, University of Louisville School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Gail F Whitman-Elia, MD, Professor, Department of Obstetrics and Gynecology, University of South Carolina School of Medicine; Frederick B Gaupp, MD, Consulting Staff, Department of Family Practice, Assumption Community Hospital; David Chelmow, MD, Professor of Obstetrics and Gynecology, Tufts University School of Medicine; Program Director, Tufts University Affiliated Hospitals OB/GYN Residency Program; Chair, Tufts University Health Sciences Campus Institutional Review Board Author and Editor Disclosure Synonyms and related keywords: vasa previa, single umbilical artery, velamentous insertion, umbilical cord knots, true umbilical cord knots, false umbilical cord knots, nuchal umbilical cord, umbilical cord stricture, umbilical cord hematoma, umbilical cord thrombosis, umbilical cord cysts, true umbilical cord cysts, false umbilical cord cysts, umbilical cord varix, hemangiomas, INTRODUCTIONSection 2 of 11
  Umbilical cord complications in pregnancy are numerous, ranging from false knots, which have no clinical significance, to vasa previa, which often leads to fetal death. As prenatal ultrasound becomes increasingly sophisticated, many of these conditions are being diagnosed in utero. However, many are not apparent before delivery, and the only forewarning is related to their association with certain conditions such as monochorionic twins and placental abruption. This article outlines the risk factors for known umbilical cord complications and the available courses of action to avert their associated morbidity and mortality. CORD LENGTHSection 3 of 11
The length of the umbilical cord varies from no cord (achordia) to 300 cm, with diameters up to 3 cm. Umbilical cords are helical in nature, with as many as 380 helices. An average umbilical cord is 55 cm long, with a diameter of 1-2 cm and 11 helices.1 For unknown reasons, most cords coil to the left.2 About 5% of cords are shorter than 35 cm, and another 5% are longer than 80 cm.3 Causes of differences in cord length are unknown, however the length of the cord is thought to reflect movement of the fetus in utero. Short cords are associated with fetal movement disorders and intrauterine constraint, as well as placental abruption and cord rupture. Excessively long cords are associated with fetal entanglement, true knots, and thrombi.1 Assessing cord length prenatally is not possible. Straight cords with few or absent helices have been associated with adverse fetal outcomes.1 In cases of placental abruption, oligohydramnios, or breech presentation, consideration may be given to measurement and documentation of cord length after birth, because an abnormal cord length argues for a long-term fetal condition. SINGLE UMBILICAL ARTERYSection 4 of 11
The umbilical cord normally contains 2 arteries and a single vein. Occasionally, one umbilical artery is absent, with the left artery absent more commonly than the right. Single umbilical arteries are associated more commonly with fetal anomalies than normal cords. Single umbilical artery occurs in fewer than 1% of cords in singletons and 5% of cords in at least one twin. Single umbilical artery also occurs more often in fetal demise than in live births.4 The incidence can be overestimated with gross examination of the cord, especially if the portion close to the placenta is examined, because the arteries may fuse close to the placenta.5 Single umbilical arteries are found twice as often in white women than in African American and Japanese women. Diabetes increases the risk significantly. The male-to-female ratio is 0.85:1. Single umbilical artery is believed to be caused by atrophy of a previously normal artery, presence of the original artery of the body stalk, or agenesis of one of the umbilical arteries. The vessels in the cord are clearly identifiable with ultrasonography. The vein is usually larger than the arteries. Single umbilical artery may be diagnosed prenatally with the finding of only 2 vessels on a cross section of the cord, or a vessel seen on only 1 side of the fetal bladder. Prenatal diagnosis of a single umbilical artery should prompt examination for other anomalies. Because associated anomalies can occur in any organ system, consider a detailed anatomy survey whenever a 2-vessel cord is discovered. Fetal echocardiogram may also be helpful. Consider fetal karyotyping, especially if anomalies are found. Because some studies have reported an association with fetal growth retardation, consider third trimester ultrasonography for fetal growth.10 Consider neonatal ultrasonography to examine for renal anomalies. VELAMENTOUS INSERTION AND VASA PREVIASection 5 of 11
Velamentous insertion With velamentous insertion, the umbilical cord inserts into the chorion laeve at a point away from the placental edge, and the vessels pass to the placenta across the surface of the membranes between the amnion and the chorion. One percent of singletons have velamentous insertion; however, this condition occurs in almost 15% of monochorionic twins12 and is common in triplets. Velamentous insertion occurs (1) when placental tissue grows laterally, leaving the centrally located umbilical cord in an area that becomes atrophic, or (2) when the cord implants in the trophoblast anterior to the decidua capsularis rather than the trophoblast tissue that is destined to become the placental mass. Velamentous insertion has been diagnosed by ultrasonography with a sensitivity of 67% and specificity of 100% in the second trimester13; first trimester diagnosis is also possible14. The condition is associated with a lower maternal serum alpha-fetoprotein (AFP) and higher maternal serum human chorionic gonadotropin (hCG).15, 16 Velamentous insertion can cause hemorrhage if the vessels are torn when the membranes are ruptured, most often with a vasa previa (see below). Velamentous insertion of the cord is associated with low birth weight, prematurity, and abnormal fetal heart patterns in labor.17, 18 Vasa previa occurs when the fetal vessels in the membrane are situated in front of the presenting part of the fetus. This may occur because of a velamentous insertion of the cord or with vessels running between the placenta and a succenturiate lobe. Vasa previa may also exist over the dividing membrane when a second twin has a velamentous insertion of the umbilical cord. This condition occurs in 1 per 2000-3000 deliveries. The cause of vasa previa is unknown. Vasa previa may be associated with low-lying placenta, placenta with accessory lobes, and with multiple pregnancies.19 Vasa previa occasionally may be felt on palpation and ultrasonographic detection has been reported.20, 21 Color Doppler ultrasonography can be used to visualize the course of the vessels, and pulse Doppler ultrasonography can be used to confirm the fetal origin. A series of gray lines in the vicinity of the internal os may be diagnostic of vasa previa. A sinusoidal fetal heart pattern, fetal bradycardia, or fetal heart rate decelerations during labor may all indicate a ruptured vasa previa.19 A Kleihauer-Betke or Apt test may detect the presence of fetal cells in the vaginal discharge; however, in the face of a ruptured vasa previa, fetal distress is usually apparent before the test results become available. Cesarean delivery is the preferred mode of delivery for known vasa previa after confirming fetal lung maturity and is mandatory if significant vaginal bleeding occurs.21 Prenatal diagnosis of vasa previa can markedly improve outcome. In one report, pregnancies diagnosed prenatally had a 97% fetal survival as compared with 48% in those not diagnosed prenatally.19 Consider endovaginal color flow Doppler ultrasonography to rule out vasa previa for patients with a known succenturiate lobe or velamentous insertion of the cord. CORD KNOTS, NUCHAL CORD, AND CORD STRICTURESection 6 of 11
Cord knots True knots and false knots can form in the umbilical cord. True knots occur in approximately 1% of pregnancies, with the highest rate occurring in monoamnionic twins. False knots (kinks in the umbilical cord vessels) are more common. True knots have been reported to lead to a 4-fold increase in fetal loss, presumably because of compression of the cord vessels when the knot tightens. False knots have no known clinical significance. Detection of umbilical knots has been reported with ultrasonographic imaging. Prenatal diagnosis has occurred largely in monoamniotic twins, when the condition was specifically sought.22, 23 A cesarean delivery may be considered if a diagnosis of a true cord knot is made. The usefulness of antenatal testing in the followup of pregnancies with this condition is uncertain.24 Nuchal cord The cord may become coiled around various parts of the body of the fetus, usually around the neck. Nuchal cord is caused by movement of the fetus through a loop of cord. One loop around the neck occurs in approximately 20% of cases25, and multiple loops occur in up to 5% of pregnancies26. Nuchal cord has been associated with labor induction and augmentation, prolonged second stage of labor, and fetal heart rate abnormalities. Cord stricture Cord stricture is constriction or occlusion of the cord. This condition is found in 19% of fetal demises.29 Familial recurrence of umbilical cord strictures has been described.30 The etiology of umbilical cord stricture is unknown. There is a deficiency in Wharton Jelly in the umbilical cord in the area of stricture, however this could be a postmorbid change. Most infants with cord stricture are stillborn. CORD HEMATOMA, CORD CYSTS, AND CORD VARIXSection 7 of 11
Cord hematoma A cord hematoma is extravasation of blood into the Wharton jelly surrounding the umbilical cord vessels. This condition is rare in live-born infants. Cord hematoma can occur after the rupture of a varix of the umbilical vein, with subsequent effusion of blood into the cord. Invasive prenatal procedures can also cause hematomas. Finally, cord hematoma can occur spontaneously and in association with cord cysts. The vein-to-artery ratio is 1:9. Cord hematoma has been described as a cause of acute fetal distress.31, 32 A more chronic presentation of a cord hematoma may appear as a mass in the umbilical cord. Doppler studies can evaluate a suspected hematoma, which increases vascular resistance.33 If the diagnosis of cord hematoma is confirmed with a stable fetus, an amniocentesis may be performed, and delivery can be undertaken when the fetus is documented to be mature. Cord cysts Cord cysts can be defined as true or false cysts, and they can occur at any location along the cord. They are irregular in shape and are located between the vessels. Cysts are found in 0.4% of pregnancies.34 True cysts are small remnants of the allantois (ie, allantoid cysts) or the umbilical vesicle. Cysts have an epithelial lining, occur at the fetal end of the cord, and usually resolve during the first trimester. True cysts can be associated with hydronephrosis, patent urachus35, omphalocele34, and Meckel diverticulum. Persistent cysts may be observed with fetal karyotyping and level 2 second trimester ultrasonography. In patients with large cysts, cesarean delivery undertaken as soon as fetal lung maturity is achieved may help to avoid fetal damage from cyst rupture during labor.37 Cord varix Cord varix is a cystic dilatation that can occur in any portion of the umbilical vein. Cord varix rarely occurs, and its cause is unknown. Color Doppler flow studies show very turbulent flow through the cyst, which is continuous with the umbilical vein. HEMANGIOMAS AND TERATOMASSection 8 of 11
Hemangiomas Hemangiomas are hyperechogenic masses that are found mainly at the placental end of the cord. Hemangiomas rarely occur. Hemangiomas are tumors of the endothelial cells of the vessels of the umbilical cord. They can be up to 15 cm in diameter and consist of a nodule of endothelial cells surrounded by edema and degenerated Wharton jelly. A fusiform mass in the cord may be visible with ultrasonography, but the appearance is not specific for hemangioma. These tumors have been associated with polyhydramnios and fetal hydrops.39 AFP levels tend to be high with hemangiomas.40, 39 In the presence of a suspected cord tumor, monitoring for interval growth, fetal hydrops, and fetal well-being throughout pregnancy should be considered. As cord tumors cannot be reliably distinguished prior to delivery, monitoring for vascular compression by an enlarging tumor may also be of benefit, although this complication is not associated with hemangioma per se. Teratomas Teratomas are germ cell tumors that are found at any location along the cord and have structures derived from all 3 germ cell layers. Teratomas are rare.41 They arise from germ cells in the wall of the gut that evaginate into the umbilical cord. Teratomas are differentiated from an acardiac twin because an acardiac twin has some recognizable anatomic structures, whereas the teratoma is totally disorganized. This condition cannot be specifically diagnosed prenatally. Ultrasonography may reveal an umbilical cord mass.42 Obstetric management for an umbilical cord tumor is described above. CORD PROLAPSESection 9 of 11
If the umbilical cord presents in front of the fetal presenting part and the membranes rupture, the risk that the cord will prolapse through the cervix into the vagina is significant. Occult prolapse occurs when the cord lies alongside the presenting part. Cord prolapse occurs in 0.6% of deliveries. The risk is increased with fetal malpresentations, especially when the presenting part does not fill the lower uterine segment, as is the case with incomplete breech presentations (5-10%), premature infants, and multiparous women.43 Causes include abnormal presentation, a long umbilical cord, polyhydramnios, prematurity, and an unengaged presenting part. Loops of cord in front of the presenting part can be visualized using color Doppler studies. During the course of labor, fetal bradycardia may indicate compression of a prolapsed cord, which should be ruled out with a vaginal examination. In the presence of intact membranes, the prolapsed cord may resolve spontaneously or may be reduced by the presenting part at the onset of labor. In some cases, manual reduction of the cord has been reported with vaginal delivery and a good fetal result. In the presence of ruptured membranes, a cord prolapse can cause an obstetrical emergency requiring an immediate vaginal delivery or a cesarean delivery at the first sign of fetal distress.43 ACKNOWLEDGMENTSSection 10 of 11
The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Brian LG Morgan, MD, PhD, to the development and writing of this article. REFERENCESSection 11 of 11
Umbilical Cord Complications excerpt Article Last Updated: Aug 15, 2007 |
