| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ORIGINAL RESEARCH |
From the Department of Obstetrics, Gynecology, and Reproductive Sciences, Division of Ultrasound, Magee-Womens Hospital, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Address reprint requests to: Lyndon M. Hill, MD, Division of Ultrasound, Magee-Womens Hospital, 300 Halket Street, Pittsburgh, PA 15213; E-mail: lhill2{at}mail.magee.edu.
 |
ABSTRACT |
|---|
TOP
 ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
METHODS: The ultrasound and pathology databases were collated between January 1, 1999, and December 31, 2000. Only those cases with ultrasound and pathology information concerning the number of vessels in the umbilical cord were included for analysis (group 1). In addition, 27 cases with a two-vessel umbilical cord were included from the ultrasound database before January 1, 1999, for which pathologic information was also obtained (group 2).
RESULTS: A total of 1295 ultrasound/pathology reports were entered from January 1, 1999, through December 31, 2000; 268 cases did not have complete information, leaving 1027 for analysis (group 1). The visualization rate of the number of vessels in the umbilical cord increased from 15 to 17 weeks’ gestation (74.1–97.6%; P < .001). The visualization rate remained stable from 17.0 to 35.9 weeks’ gestation, and then declined to 83.3% (P < .01). The sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of a two-vessel umbilical cord were 85%, 99.7%, 85%, and 99.7%, respectively.
CONCLUSION: The detection rate of either a two-vessel or three-vessel umbilical cord is best achieved between 17 and 36 weeks’ gestation. In the majority of two-vessel umbilical cords that were called three-vessel, an appropriate transverse image of the umbilical cord was not obtained.
The umbilical arteries originate from the right and left common iliac arteries. Pathology studies have shown that embryos have a 0.1% incidence of a single umbilical artery ( Tanimura T. Abnormality of embryos and their membranes (abstract). Teratology 1997;16:86), whereas the rate is approximately 0.63–1% at term.1–3 This discrepancy in prevalence supports the theory that umbilical artery atrophy results in a two-vessel umbilical cord. Vesalius (1514–64) was one of the first to recognize the absence of one of the umbilical arteries.4 In a retrospective pathologic review of placentas and umbilical cords, Benirschke and Brown5 first noted the relationship between a two-vessel umbilical cord and congenital anomalies.
The purpose of our investigation was two-fold: 1) to determine the detection rate of two-vessel and three-vessel umbilical cords from 15 to 40 weeks’ gestation; and 2) to determine the sensitivity/specificity of transabdominal sonography in the detection of a two-vessel umbilical cord.
|
MATERIALS AND METHODS |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The ultrasound data was cross-referenced with the Department of Pathology’s assessment of the placenta and umbilical cord after delivery. The pathologist microscopically evaluated two cross-sections of the umbilical cord to determine the number of vessels present. The study was approved by the hospital’s Institutional Review Board.
A histogram was plotted for the visualization rate of two- and three-vessel umbilical cords by gestational age. Data are expressed as mean and median with ranges. Statistical analysis was performed using the 
2 test, with P < .05 considered statistically significant.
The study group was a mixed high- and low-risk pregnancies. The maternal and fetal complications are outlined in Table 1
. Some patients had more than one complication, and 55.4% of the study group was low risk.
|
Sonographic examinations were performed with a 3.5-or a 5.0-MHz curvilinear transducer (General Electric RT3200 Advantage II, Logic 500, Logic 700, General Electric Corp., Milwaukee, WI).
A transverse view of the umbilical cord was required to determine the number of vessels in the umbilical cord. Color Doppler and the number of vessels around the bladder were not used to determine the number of umbilical cord vessels.
|
RESULTS |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
.
|
Figure 1 outlines the visualization rate of three-vessel and two-vessel umbilical cords by gestational age for 1027 cases in group 1. The number of cases evaluated at each gestational age on the bar graph is also provided. Because the number of vessels in the umbilical cord was not visualized in 43 cases, the prevalence of a two-vessel cord for group 1 was 2% (20 of 984). The visualization rate of the number of vessels in the umbilical cord increased from 15 (74.1%) to 17 (97.6%) weeks’ gestation (P < .001, confidence interval 89.5%, 98.5%). The rate then remained stable until 35.9 weeks’ gestation. The visualization rate of the number of vessels in the umbilical cord then declined to 83.3% between 36 to 40 weeks’ gestation (P < .01) (Table 3).
|
|
Of the 47 two-vessel umbilical cords (20 in group 1, 27 in group 2), 39 were correctly identified (83%), and eight were called three-vessel cords between 18.1 and 23.3 weeks’ gestation (three in group 1, five in group 2). One case had cross-sectional images of both a two-vessel and a three-vessel umbilical cord (Figure 2A and 2B). One case had a clearly identified cross-sectional image of a three-vessel cord, suggesting that this case might also have had sections of cord with two and three vessels. In the remaining six cases, a diagnosis of a three-vessel cord was made on only longitudinal images; there were no cross-sectional images of the umbilical cord.
|
There were 19 congenital anomalies in 11 of 47 (23.4%) fetuses with a two-vessel umbilical cord (group 1 and group 2). There were no major anomalies associated with a two-vessel umbilical cord that were missed on antenatal sonography. None of the 47 fetuses with a two-vessel umbilical cord were karyotypically abnormal.
|
DISCUSSION |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Previous investigations of two-vessel umbilical cords have approached their analysis from two perspectives: a pathologic evaluation of the umbilical cord,1–7 or the sonologist’s detection of a two-vessel umbilical cord.8–14 Hence, the specificity and false-negative rate of sonography in detecting a two-vessel cord could not be determined. Our study is unique in that we had pathologic and sonographic information on all of the umbilical cords (both two-vessel and three-vessel) evaluated during the study period. Our data on sensitivity, specificity, false-positive rate, and false-negative rate can be used by our facilities to assess their success at visualizing two-vessel umbilical cords.
A single umbilical artery has been noted more frequently in young primiparous and older multiparous women.7 The incidence of a single umbilical artery in prospective pathologic series ranges from 6.08% to 1.9%. In the first and second trimesters, the incidence of a two-vessel umbilical cord ranges from 0.2% to 2.03%.3 Our results are consistent with these reports.
Umbilical artery fusion may occur along the umbilical cord.15,16 We documented one such case and suspect that there were at least four additional cases of intermittent umbilical artery fusion along the cord. Umbilical artery fusion does not have the same significance as a two-vessel cord.3 Hence, if both two-vessel and three-vessel cords are identified, the patient should be considered to have a normal three-vessel umbilical cord.
The neonatal prognosis associated with a two-vessel umbilical cord is primarily determined by the increased prevalence of fetal and placental malformations.8,17,18 Some studies have also found an increased prevalence of small-for-gestational-age fetuses associated with a single umbilical artery.3,18–20 However, the association between growth restriction and a two-vessel umbilical cord remains controversial.9 The stillbirth rate appears to be increased in anatomically normal fetuses with a two-vessel umbilical cord.3,21 Trisomy 13 and 18 are the most common karyotypic abnormalities associated with a two-vessel umbilical cord.22,23 In one study of ten karyotypically abnormal fetuses with a two-vessel umbilical cord, all but one had additional anatomic defects on ultrasound.22 In the absence of additional anomalies or intrauterine growth restriction, an isolated single umbilical artery may not affect neonatal outcome.8,10
Jassani et al24 reported the first sonographic diagnosis of a two-vessel umbilical cord in 1980. The sonographic assessment of the umbilical cord is best achieved on transverse section. Our data are consistent with this suggestion – six cases that were incorrectly called a three-vessel, rather than a two-vessel umbilical cord, were only imaged longitudinally.
Gestational age has an affect upon the ability to appropriately visualize the vessels in the umbilical cord. In difficult cases (ie, maternal obesity, decreased amniotic fluid volume, etc), color Doppler is occasionally helpful.25,26 This modality has been used to assess the number of vessels in a free loop of umbilical cord, as well as the number of vessels around the fetal bladder. However, Bornemeier et al11 have reported that in 14% of cases with a two-vessel umbilical cord in the amniotic fluid, two, rather than one vessel, were adjacent to the fetal urinary bladder. These authors only evaluated fetuses with a two-vessel umbilical cord. In our assessment of three-vessel umbilical cords, we found another configuration – three vessels on a transverse section of the umbilical cord, but only one vessel around the fetal bladder (Figure 3A and 3B). The findings of Bornemeier et al11 and the results of our investigation indicate that the number of vessels visualized around the fetal bladder does not accurately determine the number of vessels in the umbilical cord. Furthermore, all of the data on the association between the two-vessel umbilical cord and perinatal outcome is based upon the evaluation of the umbilical cord, not upon the number of vessels around the bladder.
|
Our study indicates that ultrasound is highly specific for the detection of a two-vessel umbilical cord. Based upon the results of our study, we would recommend that the number of vessels in the umbilical cord be assessed on a transverse image of the umbilical cord within the amniotic fluid whenever possible. This is most effectively performed between 17.0 and 35.9 weeks’ gestation.
|
Footnotes |
|---|
Received February 16, 2001. Received in revised form July 16, 2001. Accepted July 19, 2001.
|
REFERENCES |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
2. Vlietinck RF, Thiery R, Orye E, DeClercq A, VanVaernbergh P. Significance of the single umbilical artery. A clinical, radiological, chromosomal, and dermatoglyphic study. Arch Dis Child 1972;47:639–42.
3. Heifetz SA. Single umbilical artery. A statistical analysis of 237 autopsy cases and review of the literature. Perspect Ped Path 1984;8:345–78.
4. Lenoski EF, Medovy H. Single umbilical artery: Incidence, clinical significance and relation to autosomal trisomy. Canad Med Assoc J 1962;87:1229–31.
5. Benirschke K, Brown WH. A vascular anomaly of the umbilical cord: The absence of one artery in the umbilical cord of normal and abnormal fetuses. Obstet Gynecol 1955;6:399–404.
6. Fujikura T. Single umbilical artery and congenital malformations. Am J Obstet Gynecol 1964;88:829–30.
7. Leung AKC, Robson WLM. Single umbilical artery. Am J Dis Child 1989;143:108–11.[Abstract]
8. Geipel A, Germer V, Welp T, Schwinger E, Gembruch U. Prenatal diagnosis of single umbilical artery: Determination of the absent side, associated anomalies, Doppler findings and perinatal outcome. Ultrasound Obstet Gynecol 2000;15:114–7.[Medline]
9. Abuhamad AZ, Shaffer W, Mani G, Copel JA, Hobbins JC, Evans AT. Single umbilical artery: Does it matter which artery is missing? Am J Obstet Gynecol 1995;173: 728–32.[Medline]
10. Parilla BV, Tamura RK, MacGregor SN, Geibel LJ, Sabbagha RE. The clinical significance of a single umbilical artery as an isolated finding on prenatal ultrasound. Obstet Gynecol 1995;85:570–2.[Abstract]
11. Bornemeier S, Carpinito LA, Winter TC. Sonographic evaluation of the two vessel umbilical cord. A comparison between umbilical arteries adjacent to the bladder and cross-sections of the umbilical cord. J Diagn Med Sonogr 1996;12:260–5.
12. Jones TB, Sorokin Y, Bhatia R, Zador IE, Bottoms SG. Single umbilical artery: Accurate diagnosis? Am J Obstet Gynecol 1993;169:538–40.[Medline]
13. Wu M-H, Chang F-M, Shen M-R, Yao B-L, Chang C-H, Yu C-H, et al. Prenatal sonographic diagnosis of single umbilical artery. J Clin Ultrasound 1997;25:425–30.[Medline]
14. Catanzarite VA, Hendricks SK, Maida C, Westbrook C, Cousins L, Schrimmer D. Prenatal diagnosis of the two-vessel cord: Implications for patient counselling and obstetric management. Ultrasound Obstet Gynecol 1995; 5:98–105.[Medline]
15. Rosenak D, Meizner I. Prenatal sonographic detection of single and double umbilical artery in the same fetus. J Ultrasound Med 1994;13:995–6.[Medline]
16. Sepulveda W, Dezerega V, Carstens E, Gutierrez J. Fused umbilical arteries. Prenatal sonographic diagnosis and clinical significance. J Ultrasound Med 2001;20:59–62.[Abstract]
17. Nyberg DA, Mahony BS, Luthy D, Kapur R. Single umbilical artery. Prenatal detection of concurrent anomalies. J Ultrasound Med 1991;10:247–53.[Abstract]
18. Bryan EM, Kohler HG. The missing umbilical artery. I. Prospective study based on a maternity unit. Arch Dis Child 1974;49:844–52.[Medline]
19. Bjøro K. Vascular anomalies of the umbilical cord. II. Perinatal and pediatric implications. Early Hum Dev 1983; 8:279–87.[Medline]
20. Rinehart BK, Terrone DA, Taylor CW, Isler CM, Larmon JE, Roberts WE. Single umbilical artery is associated with an increased incidence of structural and chromosomal anomalies and growth restriction. Am J Perinatol 2000;17:229–32.[Medline]
21. Clausen I. Umbilical cord anomalies and antenatal fetal deaths. Obstet Gynecol Surv 1989;44:841–5.[Medline]
22. Khang TY, George K. Chromosomal abnormalities associated with a single umbilical artery. Prenat Diagn 1992; 12:965–8.[Medline]
23. Saller DN, Keene CL, Sun CCJ, Schwartz S. The association of single umbilical artery with cytogenetically abnormal pregnancies. Am J Obstet Gynecol 1990;163:922–5.[Medline]
24. Jassani MN, Brennan JN, Merkatz IR. Prenatal diagnosis of a single umbilical artery by ultrasound. J Clin Ultrasound 1980;8:447–8.[Medline]
25. Jauniaux E, Campbell S, Vyos S. The use of color Doppler imaging for prenatal diagnosis of umbilical cord abnormalities: Report of three cases. Am J Obstet Gynecol 1989; 161:1195–7.[Medline]
26. Jeanty P. Fetal and funicular vascular anomalies: Identification with prenatal ultrasound. Radiology 1989;173: 367–70.
This article has been cited by other articles:
|
|
 |
|
  D. R. Gossett, M. E. Lantz, and C. A. Chisholm Antenatal Diagnosis of Single Umbilical Artery: Is Fetal Echocardiography Warranted? Obstet. Gynecol., November 1, 2002; 100(5): 903 - 908. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
