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Prenatal diagnosis and obstetrical management of umbilical cord abnormalities

Waldo Sepulveda, MD
Neil J Sebire, FRCP
Section Editors
Deborah Levine, MD
Susan M Ramin, MD
Deputy Editor
Vanessa A Barss, MD, FACOG


The fetus obtains all of its nutrients and oxygen and eliminates carbon dioxide and most waste products via the umbilical cord, thus it is a critical organ during prenatal life. Despite this, it is a relatively simple and unprotected structure containing two arteries and one vein surrounded by a gelatinous stroma (Wharton’s jelly) and covered by a single layer of amnion.

The umbilical arteries transport deoxygenated blood and wastes from the fetus to the placenta. They are branches of the internal iliac artery that curve around the fetal bladder, eventually becoming adjacent to one another at the umbilicus. At that point, they exit the fetus and course along the length of the cord, usually in a helicoidal fashion surrounding the umbilical vein, finally separating at the placenta, where they divide into chorionic arteries on the surface of the chorionic plate and form perforating branches to the underlying villi (figure 1).

The left umbilical vein is formed at the chorionic plate by the confluence of chorionic veins, and transports oxygenated blood and nutrients back to the fetus. In the fetal abdomen, it runs cephalad from the cord insertion site until it enters the liver, where it anastomoses with the left portal vein (figure 2). The right umbilical vein usually degenerates very early in embryogenesis, but rarely persists as the only umbilical vein [1,2] or as a fourth umbilical vessel (see 'Supernumerary vessels' below).

The intraabdominal portions of the umbilical vessels degenerate after birth; the umbilical arteries become the lateral ligaments of the bladder and the umbilical vein develops into the round ligament of the liver.

This topic will review the most important aspects of the structural abnormalities of the umbilical cord, as determined by prenatal ultrasound. The gross anatomy and histology of the umbilical cord are discussed separately. (See "Gross examination of the placenta", section on 'Umbilical cord' and "The placental pathology report", section on 'Umbilical cord'.)


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  1. Shen O, Tadmor OP, Yagel S. Prenatal diagnosis of persistent right umbilical vein. Ultrasound Obstet Gynecol 1996; 8:31.
  2. Jeanty P. Persistent right umbilical vein: an ominous prenatal finding? Radiology 1990; 177:735.
  3. Hill LM, Kislak S, Runco C. An ultrasonic view of the umbilical cord. Obstet Gynecol Surv 1987; 42:82.
  4. Dudiak CM, Salomon CG, Posniak HV, et al. Sonography of the umbilical cord. Radiographics 1995; 15:1035.
  5. Sherer DM, Anyaegbunam A. Prenatal ultrasonographic morphologic assessment of the umbilical cord: a review. Part I. Obstet Gynecol Surv 1997; 52:506.
  6. Sherer DM, Anyaegbunam A. Prenatal ultrasonographic morphologic assessment of the umbilical cord: a review. Part II. Obstet Gynecol Surv 1997; 52:515.
  7. Sepulveda W. Time for a more detailed prenatal examination of the umbilical cord? Ultrasound Obstet Gynecol 1999; 13:157.
  8. Sepulveda W, Sebire NJ, Harris R, et al. The placenta, umbilical cord, and membranes. In: Diagnostic imaging of fetal anomalies. Nyberg DA, McGahan JP, Pretorius DH, Pilu G (Eds), Lippincott Williams & Wilkins, Philadelphia 2003. p.85.
  9. Hill LM, DiNofrio DM, Guzick D. Sonographic determination of first trimester umbilical cord length. J Clin Ultrasound 1994; 22:435.
  10. Bowerman RA. Sonography of fetal midgut herniation: normal size criteria and correlation with crown-rump length. J Ultrasound Med 1993; 12:251.
  11. American Institute of Ultrasound in Medicine. AIUM practice guideline for the performance of obstetric ultrasound examinations. J Ultrasound Med 2010; 29:157.
  12. Sepulveda W, Wong AE, Gomez L, Alcalde JL. Improving sonographic evaluation of the umbilical cord at the second-trimester anatomy scan. J Ultrasound Med 2009; 28:831.
  13. Ghezzi F, Raio L, Günter Duwe D, et al. Sonographic umbilical vessel morphometry and perinatal outcome of fetuses with a lean umbilical cord. J Clin Ultrasound 2005; 33:18.
  14. Eddleman KA, Lockwood CJ, Berkowitz GS, et al. Clinical significance and sonographic diagnosis of velamentous umbilical cord insertion. Am J Perinatol 1992; 9:123.
  15. de Laat MW, Franx A, van Alderen ED, et al. The umbilical coiling index, a review of the literature. J Matern Fetal Neonatal Med 2005; 17:93.
  16. Persutte WH, Hobbins J. Single umbilical artery: a clinical enigma in modern prenatal diagnosis. Ultrasound Obstet Gynecol 1995; 6:216.
  17. Jones TB, Sorokin Y, Bhatia R, et al. Single umbilical artery: accurate diagnosis? Am J Obstet Gynecol 1993; 169:538.
  18. Benirschke K, Kaufmann P. Umbilical cord and major fetal vessels. In: Pathology of the human placenta, 2nd, Springer-Verlag, New York 1990. p.180.
  19. Rosenak D, Meizner I. Prenatal sonographic detection of single and double umbilical artery in the same fetus. J Ultrasound Med 1994; 13:995.
  20. Sepulveda W, Dezerega V, Carstens E, Gutierrez J. Fused umbilical arteries: prenatal sonographic diagnosis and clinical significance. J Ultrasound Med 2001; 20:59.
  21. Jeanty P. Fetal and funicular vascular anomalies: identification with prenatal US. Radiology 1989; 173:367.
  22. Sepúlveda WH. Antenatal sonographic detection of single umbilical artery. J Perinat Med 1991; 19:391.
  23. Sepulveda W, Peek MJ, Hassan J, Hollingsworth J. Umbilical vein to artery ratio in fetuses with single umbilical artery. Ultrasound Obstet Gynecol 1996; 8:23.
  24. De Catte L, Burrini D, Mares C, Waterschoot T. Single umbilical artery: analysis of Doppler flow indices and arterial diameters in normal and small-for-gestational age fetuses. Ultrasound Obstet Gynecol 1996; 8:27.
  25. Sepulveda W, Bower S, Flack NJ, Fisk NM. Discordant iliac and femoral artery flow velocity waveforms in fetuses with single umbilical artery. Am J Obstet Gynecol 1994; 171:521.
  26. Sepulveda W, Nicolaidis P, Bower S, et al. Common iliac artery flow velocity waveforms in fetuses with a single umbilical artery: a longitudinal study. Br J Obstet Gynaecol 1996; 103:660.
  27. Dolkart LA, Reimers FT, Kuonen CA. Discordant umbilical arteries: ultrasonographic and Doppler analysis. Obstet Gynecol 1992; 79:59.
  28. Sepulveda W, Flack NJ, Bower S, Fisk NM. The value of color Doppler ultrasound in the prenatal diagnosis of hypoplastic umbilical artery. Ultrasound Obstet Gynecol 1994; 4:143.
  29. Petrikovsky B, Schneider E. Prenatal diagnosis and clinical significance of hypoplastic umbilical artery. Prenat Diagn 1996; 16:938.
  30. Aoki S, Hata T, Ariyuki Y, et al. Antenatal diagnosis of aberrant umbilical vessels. Gynecol Obstet Invest 1997; 43:232.
  31. Raio L, Ghezzi F, Di Naro E, et al. The clinical significance of antenatal detection of discordant umbilical arteries. Obstet Gynecol 1998; 91:86.
  32. Sepulveda W, Reyes M, Gonçalves LF. Two uncommon umbilical vessel anomalies in a fetus with trisomy 18. Prenat Diagn 1998; 18:1098.
  33. Nyberg DA, Mahony BS, Luthy D, Kapur R. Single umbilical artery. Prenatal detection of concurrent anomalies. J Ultrasound Med 1991; 10:247.
  34. Altshuler G, Tsang RC, Ermocilla R. Single umbilical artery. Correlation of clinical status and umbilical cord histology. Am J Dis Child 1975; 129:697.
  35. Benirschke K, Dodds JP. Angiomyxoma of the umbilical cord with atrophy of an umbilical artery. Obstet Gynecol 1967; 30:99.
  36. Pérez-Cosio C, Sheiner E, Abramowicz JS. Four-vessel umbilical cord: not always a dire prognosis. J Ultrasound Med 2008; 27:1389.
  37. Murdoch DE. Umbilical-cord doubling. Report of a case. Obstet Gynecol 1966; 27:555.
  38. Rodriguez MA. Four-vessel umbilical cord without congenital abnormalities. South Med J 1984; 77:539.
  39. Painter D, Russell P. Four-vessel umbilical cord associated with multiple congenital anomalies. Obstet Gynecol 1977; 50:505.
  40. Beck R, Naulty CM. A human umbilical cord with four arteries. Clin Pediatr (Phila) 1985; 24:118.
  41. Gore RM, Filly RA, Parer JT. Sonographic antepartum diagnosis of conjoined twins. Its impact on obstetric management. JAMA 1982; 247:3351.
  42. Cohen HL, Shapiro ML, Haller JO, Schwartz D. The multivessel umbilical cord: an antenatal indicator of possible conjoined twinning. J Clin Ultrasound 1992; 20:278.
  43. Ghosh A, Woo JS, MacHenry C, et al. Fetal loss from umbilical cord abnormalities--a difficult case for prevention. Eur J Obstet Gynecol Reprod Biol 1984; 18:183.
  44. Clausen I. Umbilical cord anomalies and antenatal fetal deaths. Obstet Gynecol Surv 1989; 44:841.
  45. Benirschke K. Obstetrically important lesions of the umbilical cord. J Reprod Med 1994; 39:262.
  46. Heifetz SA. The umbilical cord: obstetrically important lesions. Clin Obstet Gynecol 1996; 39:571.
  47. Konstantinova B. Malformations of the umbilical cord. Acta Genet Med Gemellol (Roma) 1977; 26:259.
  48. Fortune DW, Ostör AG. Umbilical artery aneurysm. Am J Obstet Gynecol 1978; 131:339.
  49. Doehrman P, Derksen BJ, Perlow JH, et al. Umbilical artery aneurysm: a case report, literature review, and management recommendations. Obstet Gynecol Surv 2014; 69:159.
  50. Siddiqi TA, Bendon R, Schultz DM, Miodovnik M. Umbilical artery aneurysm: prenatal diagnosis and management. Obstet Gynecol 1992; 80:530.
  51. Berg C, Geipel A, Germer U, et al. Prenatal diagnosis of umbilical cord aneurysm in a fetus with trisomy 18. Ultrasound Obstet Gynecol 2001; 17:79.
  52. Sepulveda W, Corral E, Kottmann C, et al. Umbilical artery aneurysm: prenatal identification in three fetuses with trisomy 18. Ultrasound Obstet Gynecol 2003; 21:292.
  53. Shen O, Reinus C, Baranov A, Rabinowitz RR. Prenatal diagnosis of umbilical artery aneurysm: a potentially lethal anomaly. J Ultrasound Med 2007; 26:251.
  54. Sentilhes L, Vivet-Lefébure A, Patrier S, et al. Umbilical artery aneurysm in a severe growth-restricted fetus with normal karyotype. Prenat Diagn 2007; 27:1059.
  55. Weber MA, Sau A, Maxwell DJ, et al. Third trimester intrauterine fetal death caused by arterial aneurysm of the umbilical cord. Pediatr Dev Pathol 2007; 10:305.
  56. Hill AJ, Strong TH Jr, Elliott JP, Perlow JH. Umbilical artery aneurysm. Obstet Gynecol 2010; 116 Suppl 2:559.
  57. Olog A, Thomas JT, Petersen S, et al. Large umbilical artery aneurysm with a live healthy baby delivered at 31 weeks. Fetal Diagn Ther 2011; 29:331.
  58. Mahony BS, McGahan JP, Nyberg DA, Reisner DP. Varix of the fetal intra-abdominal umbilical vein: comparison with normal. J Ultrasound Med 1992; 11:73.
  59. Fung TY, Leung TN, Leung TY, Lau TK. Fetal intra-abdominal umbilical vein varix: what is the clinical significance? Ultrasound Obstet Gynecol 2005; 25:149.
  60. Byers BD, Goharkhay N, Mateus J, et al. Pregnancy outcome after ultrasound diagnosis of fetal intra-abdominal umbilical vein varix. Ultrasound Obstet Gynecol 2009; 33:282.
  61. Zalel Y, Lehavi O, Heifetz S, et al. Varix of the fetal intra-abdominal umbilical vein: prenatal sonographic diagnosis and suggested in utero management. Ultrasound Obstet Gynecol 2000; 16:476.
  62. Mankuta D, Nadjari M, Pomp G. Isolated fetal intra-abdominal umbilical vein varix: clinical importance and recommendations. J Ultrasound Med 2011; 30:273.
  63. White SP, Kofinas A. Prenatal diagnosis and management of umbilical vein varix of the intra-amniotic portion of the umbilical vein. J Ultrasound Med 1994; 13:992.
  64. Carpio RA, De Loredo R, Ochua G. Prenatal diagnosis of intramniotic umbilical vein varix (abstract). Ultrasound Obstet Gynecol 1999; 14:S55.
  65. Melcer Y, Ben-Ami I, Wiener Y, et al. Long-term outcomes of children with umbilical vein varix diagnosed prenatally. Prenat Diagn 2013; 33:492.
  66. Rempen A. Sonographic first-trimester diagnosis of umbilical cord cyst. J Clin Ultrasound 1989; 17:53.
  67. Skibo LK, Lyons EA, Levi CS. First-trimester umbilical cord cysts. Radiology 1992; 182:719.
  68. Fox H, Sebire NJ. Pathology of the umbilical cord. In: Pathology of the placenta. Major problems in pathology, 3rd, WB Saunders, London 2007. p.473.
  69. Heifetz SA, Rueda-Pedraza ME. Omphalomesenteric duct cysts of the umbilical cord. Pediatr Pathol 1983; 1:325.
  70. Persutte WH, Lenke RR, Kropp K, Ghareeb C. Antenatal diagnosis of fetal patent urachus. J Ultrasound Med 1988; 7:399.
  71. Chantler C, Baum JD, Wigglesworth JS, Scopes JW. Giant umbilical cord associated with a patent urachus and fused umbilical arteries. J Obstet Gynaecol Br Commonw 1969; 76:273.
  72. Ente G, Penzer PH, Kenigsberg K. Giant umbilical cord associated with patent urachus. An external clue to internal anomaly. Am J Dis Child 1970; 120:82.
  73. Nobuhara KK, Lukish JR, Hartman GE, Gilbert JC. The giant umbilical cord: an unusual presentation of a patent urachus. J Pediatr Surg 2004; 39:128.
  74. Wildhaber BE, Antonelli E, Pfister RE. The giant umbilical cord. Arch Dis Child Fetal Neonatal Ed 2005; 90:F535.
  75. Schaefer IM, Männer J, Faber R, et al. Giant umbilical cord edema caused by retrograde micturition through an open patent urachus. Pediatr Dev Pathol 2010; 13:404.
  76. Rosenberg JC, Chervenak FA, Walker BA, et al. Antenatal sonographic appearance of omphalomesenteric duct cyst. J Ultrasound Med 1986; 5:719.
  77. McCalla CO, Lajinian S, DeSouza D, Rottem S. Natural history of antenatal omphalomesenteric duct cyst. J Ultrasound Med 1995; 14:639.
  78. Donnenfeld AE, Mennuti MT, Templeton JM, Gabbe SG. Prenatal sonographic diagnosis of a vesico-allantoic abdominal wall defect. J Ultrasound Med 1989; 8:43.
  79. Persutte WH, Lenke RR. Disappearing fetal umbilical cord masses. Are these findings suggestive of urachal anomalies? J Ultrasound Med 1990; 9:547.
  80. Frazier HA, Guerrieri JP, Thomas RL, Christenson PJ. The detection of a patent urachus and allantoic cyst of the umbilical cord on prenatal ultrasonography. J Ultrasound Med 1992; 11:117.
  81. Sepulveda W, Bower S, Dhillon HK, Fisk NM. Prenatal diagnosis of congenital patent urachus and allantoic cyst: the value of color flow imaging. J Ultrasound Med 1995; 14:47.
  82. Tolaymat LL, Maher JE, Kleinman GE, et al. Persistent patent urachus with allantoic cyst: a case report. Ultrasound Obstet Gynecol 1997; 10:366.
  83. Yoo SJ, Lee YH, Ryu HM, et al. Unusual fate of vesicoallantoic cyst with non-visualization of fetal urinary bladder in a case of patent urachus. Ultrasound Obstet Gynecol 1997; 9:422.
  84. Fink IJ, Filly RA. Omphalocele associated with umbilical cord allantoic cyst: sonographic evaluation in utero. Radiology 1983; 149:473.
  85. Bureau M, Bolduc S. Allantoic cysts and posterior urethral valves: a case report. Ultrasound Obstet Gynecol 2011; 38:116.
  86. Battaglia C, Artini PG, D'Ambrogio G, Genazzani AR. Cord vessel compression by an expanding allantoic cyst: case report. Ultrasound Obstet Gynecol 1992; 2:58.
  87. Ross JA, Jurkovic D, Zosmer N, et al. Umbilical cord cysts in early pregnancy. Obstet Gynecol 1997; 89:442.
  88. Pal K, Ashri H, Al-Ghazal FA. Allantoic cyst and patent urachus. Indian J Pediatr 2009; 76:221.
  89. Zimmer EZ, Bronshtein M. Fetal intra-abdominal cysts detected in the first and early second trimester by transvaginal sonography. J Clin Ultrasound 1991; 19:564.
  90. Jauniaux E, Donner C, Thomas C, et al. Umbilical cord pseudocyst in trisomy 18. Prenat Diagn 1988; 8:557.
  91. Sepulveda W, Pryde PG, Greb AE, et al. Prenatal diagnosis of umbilical cord pseudocyst. Ultrasound Obstet Gynecol 1994; 4:147.
  92. Smith GN, Walker M, Johnston S, Ash K. The sonographic finding of persistent umbilical cord cystic masses is associated with lethal aneuploidy and/or congenital anomalies. Prenat Diagn 1996; 16:1141.
  93. Sepulveda W, Gutierrez J, Sanchez J, et al. Pseudocyst of the umbilical cord: prenatal sonographic appearance and clinical significance. Obstet Gynecol 1999; 93:377.
  94. Iaccarino M, Baldi F, Persico O, Palagiano A. Ultrasonographic and pathologic study of mucoid degeneration of umbilical cord. J Clin Ultrasound 1986; 14:127.
  95. Zangen R, Boldes R, Yaffe H, et al. Umbilical cord cysts in the second and third trimesters: significance and prenatal approach. Ultrasound Obstet Gynecol 2010; 36:296.
  96. Brown R, Nicolaides K. Umbilical cord hematoma associated with an umbilical cord cyst and fetal death at 28 weeks of gestation. J Ultrasound Med 2000; 19:223.
  97. Sepulveda W, Wong AE, Gonzalez R, et al. Fetal death due to umbilical cord hematoma: a rare complication of umbilical cord cyst. J Matern Fetal Neonatal Med 2005; 18:387.
  98. Hannaford K, Reeves S, Wegner E. Umbilical cord cysts in the first trimester: are they associated with pregnancy complications? J Ultrasound Med 2013; 32:801.
  99. Ghezzi F, Raio L, Di Naro E, et al. Single and multiple umbilical cord cysts in early gestation: two different entities. Ultrasound Obstet Gynecol 2003; 21:215.
  100. Sepulveda W, Leible S, Ulloa A, et al. Clinical significance of first trimester umbilical cord cysts. J Ultrasound Med 1999; 18:95.
  101. Sepulveda W, Rompel SM, Cafici D, et al. Megacystis associated with an umbilical cord cyst: a sonographic feature of a patent urachus in the first trimester. J Ultrasound Med 2010; 29:295.
  102. Clausen I, Thomsen SG. Pseudotumors of the umbilical cord and fetal membranes. Acta Obstet Gynecol Scand 1992; 71:148.
  103. Jauniaux E, Donner C, Simon P, et al. Pathologic aspects of the umbilical cord after percutaneous umbilical blood sampling. Obstet Gynecol 1989; 73:215.
  104. Ghidini A, Romero R, Eisen RN, et al. Umbilical cord hemangioma. Prenatal identification and review of the literature. J Ultrasound Med 1990; 9:297.
  105. Jauniaux E, Moscoso G, Chitty L, et al. An angiomyxoma involving the whole length of the umbilical cord. Prenatal diagnosis by ultrasonography. J Ultrasound Med 1990; 9:419.
  106. Yavner DL, Redline RW. Angiomyxoma of the umbilical cord with massive cystic degeneration of Wharton's jelly. Arch Pathol Lab Med 1989; 113:935.
  107. Wilson RD, Magee JF, Sorensen PH, Johnson A. In utero decompression of umbilical cord angiomyxoma followed by vaginal delivery. Am J Obstet Gynecol 1994; 171:1383.
  108. Miller KA, Gauderer MW. Hemangioma of the umbilical cord mimicking an omphalocele. J Pediatr Surg 1997; 32:810.
  109. Daniel-Spiegel E, Weiner E, Gimburg G, Shalev E. The association of umbilical cord hemangioma with fetal vascular birthmarks. Prenat Diagn 2005; 25:300.
  110. KREYBERG L. A teratoma-like swelling in the umbilical cord possibly of acardius nature. J Pathol Bacteriol 1958; 75:109.
  111. Smith D, Majmudar B. Teratoma of the umbilical cord. Hum Pathol 1985; 16:190.
  112. Kreczy A, Alge A, Menardi G, et al. Teratoma of the umbilical cord. Case report with review of the literature. Arch Pathol Lab Med 1994; 118:934.
  113. Satgé DC, Laumond MA, Desfarges F, Chenard MP. An umbilical cord teratoma in a 17-week-old fetus. Prenat Diagn 2001; 21:284.
  114. Hargitai B, Csabai L, Bán Z, et al. Rare case of exomphalos complicated with umbilical cord teratoma in a fetus with trisomy 13. Fetal Diagn Ther 2005; 20:528.
  115. El-Messidi A, Fung Kee Fung K. Umbilical cord hernia mimicking a cord teratoma. J Obstet Gynaecol Can 2009; 31:533.
  116. Ahmed N, Kale V, Thakkar H, et al. Sonographic diagnosis of placental teratoma. J Clin Ultrasound 2004; 32:98.
  117. Sepulveda W, Shennan AH, Bower S, Fisk NM. Discordant umbilical artery flow velocity waveforms in spontaneous umbilical cord hematoma. J Clin Ultrasound 1995; 23:330.
  118. Kurata H, Sekizuka N, Kato R, et al. Intra-amniotic maternal hemorrhage in preterm labor: a case report. J Perinat Med 1995; 23:229.
  119. Pretorius DH, Chau C, Poeltler DM, et al. Placental cord insertion visualization with prenatal ultrasonography. J Ultrasound Med 1996; 15:585.
  120. Di Salvo DN, Benson CB, Laing FC, et al. Sonographic evaluation of the placental cord insertion site. AJR Am J Roentgenol 1998; 170:1295.
  121. Sepulveda W, Rojas I, Robert JA, et al. Prenatal detection of velamentous insertion of the umbilical cord: a prospective color Doppler ultrasound study. Ultrasound Obstet Gynecol 2003; 21:564.
  122. Sebire NJ. Pathophysiological significance of abnormal umbilical cord coiling index. Ultrasound Obstet Gynecol 2007; 30:804.
  123. Qin Y, Lau TK, Rogers MS. Second-trimester ultrasonographic assessment of the umbilical coiling index. Ultrasound Obstet Gynecol 2002; 20:458.
  124. De Laat MW, Franx A, Nikkels PG, Visser GH. Prenatal ultrasonographic prediction of the umbilical coiling index at birth and adverse pregnancy outcome. Ultrasound Obstet Gynecol 2006; 28:704.
  125. Predanic M, Perni SC, Chasen ST, et al. Ultrasound evaluation of abnormal umbilical cord coiling in second trimester of gestation in association with adverse pregnancy outcome. Am J Obstet Gynecol 2005; 193:387.
  126. Degani S, Leibovich Z, Shapiro I, et al. Early second-trimester low umbilical coiling index predicts small-for-gestational-age fetuses. J Ultrasound Med 2001; 20:1183.
  127. Raio L, Ghezzi F, Di Naro E, et al. Sonographic measurement of the umbilical cord and fetal anthropometric parameters. Eur J Obstet Gynecol Reprod Biol 1999; 83:131.
  128. Ramón Y Cajal CL, Martínez RO. Prenatal diagnosis of true knot of the umbilical cord. Ultrasound Obstet Gynecol 2004; 23:99.
  129. Gembruch U, Baschat AA. True knot of the umbilical cord: transient constrictive effect to umbilical venous blood flow demonstrated by Doppler sonography. Ultrasound Obstet Gynecol 1996; 8:53.
  130. Sepulveda W, Shennan AH, Bower S, et al. True knot of the umbilical cord: a difficult prenatal ultrasonographic diagnosis. Ultrasound Obstet Gynecol 1995; 5:106.
  131. Collins JH. First report: prenatal diagnosis of a true knot. Am J Obstet Gynecol 1991; 165:1898.
  132. Hasbun J, Alcalde JL, Sepulveda W. Three-dimensional power Doppler sonography in the prenatal diagnosis of a true knot of the umbilical cord: value and limitations. J Ultrasound Med 2007; 26:1215.
  133. Hertzberg BS, Bowie JD, Bradford WD, Bolick D. False knot of the umbilical cord: sonographic appearance and differential diagnosis. J Clin Ultrasound 1988; 16:599.
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