Figure B. Tight one loop cord around the neck with a tight knot of the cord of the cord interrupting blood supply. Figure A. Umbilical cord showed clotted blood in the proximal portion. volume predisposing to free and exaggerated fetal movements ultimately leading to the entanglement of the umbilical cord with or without true umbilical cord knot. Patients undergoing amniocentesis may have a higher rate of fetal movements and uterine contractions during the procedure leading to a true knot. 3 The higher occurrence of umbilical cord knot among male fetuses might be explained by their significantly greater umbilical cord length compared to female fetuses. 6 The reason why patients with previous spontaneous abortions are prone to fatal knots is currently unknown. These risk factors were applicable to our case as she was 36 years old, grand multipara, with chronic hypertension and history of spontaneous abortion, underwent an amniocentesis and delivered a male baby who had a long umbilical cord. Umbilical cord knots are significantly associated with increased risk of several adverse perinatal and early neonatal outcomes such as non-reassuring fetal heart rate, increased occurrence of cesarean section, meconium stained amniotic fluid, cord prolapse, nuchal cord, low Apgar scores at 1 minute and fourfold increased risk of antepartum fetal death. 3,5,6 The clinical significance of low Apgar score is likely to be minor because fetal venous pH values were not affected by umbilical cord knot. 6 The exact mechanism by which the knots produce fetal demise is unknown, but could be secondary to cord vessel compression when the knot tightens. Earlier studies have not shown significant association between umbilical cord knot and fetal growth. 3,5 However, Räisänen et al found a 3.2-fold higher risk of being born small for gestational age , indicating a risk of chronic uteroplacental insufficiency in infants affected by an umbilical cord knot although the mean birth weight did not differ between the study and the control group. They explained this result by the higher occurrence of obesity and diabetes among affected pregnancies that may have masked the negative effect of umbilical cord knot on fetal growth. 6 Prenatal sonographic diagnoses of cases of a true knot of the umbilical cord have been reported infrequently. 7 Prenatal fetal surveillance, including targeted sonographic examination and Doppler studies, may be challenging as the whole length of the umbilical cord is not routinely seen. Therefore, defining a high risk group of patients that are predisposed to the formation of a true knot of the umbilical cord is important in order to increase perinatal diagnosis. A detailed US examination of the umbilical cord can reveal the hanging noose sign. Four-dimensional and color Doppler ultrasounds allow a precise diagnosis by providing a panoramic view of the umbilical cord and showing the status of the knot with regard to tension and resistance. Four-dimensional US also enable the observation of instantaneous tension exerted on the umbilical cord that, if sudden and strong, could lead to perinatal complications. 8 Conclusion Umbilical cord accidents are an important cause of stillbirth, however, not all true knots will cause fetal mortality unless it ends up in a tight knot causing uteroplacental insufficiency as an acute event. Therefore a careful evaluation of maternal history for fetal activity, fetal wellbeing is much more sensitive than the diagnostic ultrasound for the umbilical cord accidents including knots. Ultrasound studies of the umbilical cord, including insertion, composition, coiling, knotting and prolapse, should be completed. Although the frequency, predisposing factors, and potential outcomes of true knots of the umbilical cord have all been reported, the prenatal diagnosis and clinical management remains challenging, therefore, determining patients susceptible to develop this condition is important in order to increase its detection and provide the best chance of a good outcome. Ultrasound monitoring allows for early recognition of potential complications and ascertainment of fetal maturity. Acknowledgments Authors sincerely thank Dr Muhammad Aslam for performing an expert review of this article. He is an Associate Professor of Pediatrics and Director of Education and Scholarly Activities at University of California, Irvine. He is also an editorial advisory board member of the journal. References 1 Stillbirth Collaborative Research Network Writing Group. Causes of death among stillbirths. JAMA. 2011;306(22):2459- 68. 2 Spellacy WN, Gravem H, Fisch RO. The umbilical cord complications of true knots, nuchal coils, and cords around the body: report from the collaborative study of cerebral palsy. Am J Obstet Gynecol. 1966;94:1136-42. 3 Hershkovitz R, Silberstein T, Sheiner E, et al. Risk factors associated with true knots of the umbilical cord. Eur J Obstet Gynecol Reprod Biol. 2001;98:36-9. 4 Sørnes T. Umbilical cord knots. Acta Obstet Gynecol Scand. 2000; 79: 157-9. 5 Airas U, Heinonen S. Clinical significance of true umbilical knots: a population-based analysis. Am J Perinatol. 2002; 19:127-32. 6 Räisänen S, Georgiadis L, Harju M, et al. 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knot and obstetric outcome. Int J Gynaecol Obstet. 2013; 122:18-21. 7 Sherer DM, Dalloul M, Zigalo A, et al. Power Doppler and 3-dimensional sonographic diagnosis of multiple separate true knots of the umbilical cord. J Ultrasound Med. 2005: 24: 1321-3. 8 Ramon y Cajal CL, Martinez RO. Four-dimensional ultrasonography of a true knot of the umbilical cord. Am J Obset Gynecol. 2006; 195: 896-8. neonatal <strong>INTENSIVE</strong> <strong>CARE</strong> Vol. 29 No. 4 • Fall 2016 37