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Longitudinal section of the umbilical cord (case 1) near its placental end showing the two umbilical arteries (UA) and the Hyrtl anastomosis (H).
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The presence of a communicating vessel, the Hyrtl anastomosis, between the umbilical arteries is well described in pathological studies. Using different injection techniques, it has been speculated that this vessel acts as a pressure-equalizing mechanism between the different lobes of the placenta. However, its detection during fetal life has never...
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Context 1
... macroscopic peculiarity of the umbilical cord is the presence of a vessel, the Hyrtl anastomosis, connecting the umbilical arteries (Hyrtl, 1870; Benirschke and Kaufmann, 1995). In Ͼ 95% of umbilical cords some sort of anastomosis can be observed between the arteries (Young, 1972). In 90% of the cases the anastomosis is located within 1–3 cm of the placental end of the umbilical cord and varies in length from 1.5 to 2 cm and in calibre from 0.33 to 1.5 times that of the umbilical artery (Priman, 1959; Szpakowski, 1974). Although several types of interarterial anastomosis have been described (i.e. fusion of the arteries, anastomosis by two branches), the most frequent condition, accounting for Ͼ 80% of cases, is the presence of an intermediate communicating vessel between the stems of the umbilical arteries (Priman, 1959; Szpakowski, 1974). The presence of an interarterial anastomosis in the umbilical cord seems to be a recent evolutionary development. Indeed, 1890 it has not been found in lower primates (e.g. Lemurus ) (Young, 1972), while the presence of an anastomosis has been described in 30% of New World Primates ( Platyrrhine ) and in about 80% of Old World Primates ( Catarrhine ). The functional significance of the interarterial anastomosis of the umbilical cord was first described in 1870 (Hyrtl, 1870). Hyrtl speculated that its function is to equalize the blood pressure between the two arteries and to allow a uniform distribution of blood in the different regions of the placenta. It has been suggested that the Hyrtl anastomosis acts as a safety valve for the placenta (comparable to the circle of Willis for the brain) in case of compression or occlusion of one of the umbilical arteries (Priman, 1959; Benirschke and Kaufmann, 1995). In addition, it was proposed that the anastomosis plays the role of a ‘buffer’ system during uterine contractions when the blood pressure in the corresponding part of the intervillous space and cotyledons of the placenta is increased (Bacsich and Smout, 1938). The presence of a pressure-equalizing system can also explain the similar calibre of the umbilical arteries even when the territories supplied by them are of different size (Szpakowski, 1974). In this paper, we report the identification of the Hyrtl anastomosis and its functional evaluation during fetal life. A 27 year old woman, gravida 3, para 1, underwent a routine ultrasound examination at 36.4 weeks gestation. Her obstetric history was significant for a previous Caesarean section which was performed for cephalo-pelvic disproportion. The ultrasound examination was performed with a Toshiba SSH-140A unit (Toshiba Corporation, Medical Systems Division, Tokyo, Japan) equipped with a 3.75 MHz transducer. The fetal biometry and the amniotic fluid volume were appropriate for gestational age. No fetal structural abnormalities were noted. The placenta was situated on the posterior uterine wall. A targeted ultrasound revealed a three-vessel umbilical cord inserted marginally with a cross-sectional area of 202 mm 2 which is within the normal range for gestational age (Raio et al ., 1999). The diameters of the arteries were 4.2 and 4.3 mm respectively, while the diameter of the vein was 8.4 mm. The Hyrtl anastomosis connecting the stems of the umbilical arteries was identified close to the placental surface (Figure 1). The diameter of the anastomosis was 3.2 mm. The characteristic of the umbilical arteries blood flow was assessed by pulsed Doppler before (fetal side) and after (placental side) the interarterial anastomosis. The resistance indices before and after the Hyrtl anastomosis were 0.59 and 0.67 for one artery and 0.56 and 0.57 for the other artery. The umbilical artery resistance indices differed, being lower on the fetal than on the placental side (0.03 versus 0.10 respectively). The resistance index of the Hyrtl anastomosis was 0.62 (Figure 2). Colour Doppler analysis revealed that the direction of the blood flow in the anastomosis was from the umbilical artery with higher resistance to that with lower resistance. The patient delivered a 3230 g male infant by elective Caesarean section at 38.7 weeks gestation. The placental weight was 750 g and a macroscopically normal umbilical cord, 53 cm long, was inserted marginally. The presence of an oblique interarterial anastomosis crossing over the umbilical vein was confirmed macroscopically after delivery within 2 cm of the placental surface. The length of the Hyrtl anastomosis was ~16 mm. A 35 year old woman, gravida 2, para 1, was referred for an ultrasound examination at 34.3 weeks gestation because of an increased amniotic fluid volume. The patient did not have risk factors for diabetes. The ultrasound examination was performed with an Aloka Prosound 5500 unit (Aloka, Tokyo, Japan) equipped with a 3.5 MHz transducer. The fetal biometry was appropriate for gestational age and no fetal anatomical abnormalities were observed. The amniotic fluid index was 27 cm. A detailed examination of the placenta and the umbilical cord was carried out. The placenta was inserted on the left uterine wall and the umbilical cord had a central insertion. The umbilical cord had three vessels and its cross-sectional area was 189 mm 2 . The umbilical artery diameter was 2.9 mm in both vessels and the vein diameter was 8.1 mm. A cross- sectional scan of the umbilical cord close to the placental surface revealed the presence of a fourth vessel 1.6 mm diameter which represented the Hyrtl anastomosis (Figure 3). Doppler examination of the umbilical arteries was performed before and after the interarterial communicating vessel. The pulsatility index of the two arteries was 0.78 and 0.80 respectively on the fetal side and 0.80 and 0.85 on the placental side. Also in this case, the umbilical artery pulsatility indices were higher after than before the anastomosis (0.05 versus 0.02). Doppler flow velocimetry of the Hyrtl anastomosis showed a pulsatility index of 0.86. Colour Doppler assessment of the anastomosis revealed a unidirectional blood flow. The patients delivered spontaneously at 40.5 weeks of gestation a 3680 g male infant. The placental weight was 680 g while the umbilical cord length was 63 cm. Macroscopic examination of the umbilical cord revealed the presence of a communicating 1891 vessel 12 mm long at about 1 cm from the placental surface (Figure 4). In this case, the Hyrtl anastomosis emerged at right angles from the umbilical arteries. A Medline search was conducted on studies published between 1966 and February 1999 to identify whether the anastomosis between the umbilical arteries has been investigated during fetal life. Although a case of fusion between umbilical arteries before entering the placenta has been previously diagnosed at ultrasound (Rosenak and Meizner, 1994), the cases reported here are the first two of prenatal identification and Doppler assessment of the Hyrtl anastomosis. Several authors have described the presence of this vessel and speculated on its function during pregnancy (Benirschke and Kaufmann, 1995). However, these investigations were conducted after delivery studying the placenta and the umbilical cord and relating their morphology to that of the Hyrtl anastomosis. It has been demonstrated that in case of transverse anastomosis, the areas of the placenta supplied by the umbilical arteries is nearly equal (Priman, 1959). In this type of anastomosis blood can flow, if needed, in both directions. On the contrary, in oblique anastomosis there is a distinct difference in the size of the areas of the placenta supplied by each umbilical artery (Szpakowski, 1974). The artery into which the anastomosis empties supplies a larger area of the placenta, the size of which is proportional to the diameter of the Hyrtl anastomosis, and the angle of the junction is more acute. Using corrosion techniques, it has been demonstrated that there are no signs of peripheral anastomosis between the branches of the umbilical arteries except at the level of the Hyrtl anastomosis. (Bacsich and Smout, 1938). Moreover, it is possible to fill the entire arterial system of the placenta 1892 through one umbilical artery in all specimens in which an anastomosis is present (Shordania, 1929). With regard to the function of the Hyrtl anastomosis during pregnancy, it has ...
Citations
... [10][11][12] There are studies in the literature which detected the umbilical artery discordance by ultrasonography and/or histopathology, associated it with placental and umbilical cord pathologies, and compared the perinatal outcomes; however, no study was found to examine the discordance in cases with umbilical cord entanglement. [10,[12][13][14] The present study aimed to examine the histopathological diagnosis of the umbilical artery discordance in cases with single or multiple umbilical cord entanglement and its effects on pregnancy outcomes. ...
... [3] Some factors such as Hyrtl's anastomosis and compensation mechanism between arteries may protect against poor obstetrics outcomes; but on the other hand, discordance may accompany fetal abnormalities. [10,[12][13][14] In 14 cases, >1 mm umbilical arteries discordance were detected between 24 and 42 weeks of gestation, but no negative effects on 5-minute Apgar scores of the neonates was observed and explained as discordance being less and was compensated by the functional artery. [13] Similarly, discordance was detected between umbilical arteries (large 1.8±0.3 and small 1. ogy and explained as presence of Hyrtl's anastomosis. ...
... [10,[12][13][14] In 14 cases, >1 mm umbilical arteries discordance were detected between 24 and 42 weeks of gestation, but no negative effects on 5-minute Apgar scores of the neonates was observed and explained as discordance being less and was compensated by the functional artery. [13] Similarly, discordance was detected between umbilical arteries (large 1.8±0.3 and small 1. ogy and explained as presence of Hyrtl's anastomosis. [10] On the other hand, in 12 cases with trisomy 18, intrauterine growth retardation, pulmonary stenosis, maternal diabetes and hypoplastic umbilical artery were detected by ultrasonography. ...
Objective: The present study aimed to examine the histopathological diagnosis of the umbilical artery discordance in cases with single
or multiple umbilical cord entanglement and pregnancy outcomes.
Methods: The vascular structure of the umbilical cord, histopathological findings of the placenta and obstetric outcomes were retrospectively examined in 50 cases. The cases were divided into two groups by the
number of cord entanglement (single-multiple) and their histopathological findings and neonatal Apgar scores were assessed.
Results: Out of 50 cases, 38 (76%) had single and 12 (24%) had multiple cord entanglement. In 50 cases, the mean gestational age was
39.16±1.06 weeks, neonatal Apgar scores were 8.7±0.58 at 1 minute
and 9.64±0.56 at 5 minute. No statistically significant difference was
detected between single and multiple groups in terms of gestational
age (p=0.79), 1-minute Apgar score (p=0.832) and 5-minute Apgar
score (p=0.656). In histopathological examination, the diameters of
umbilical arteries 1 and 2 were found to be 0.11±0.12, 0.09±0.05 μm,
respectively in the single group (p=0.756) and 0.13±0.14, 0.06±0.02
μm, respectively in the multiple group (p=0.131). When the umbilical
arterial diameters were compared by group, the diameter of the
umbilical artery 2 was detected 0.09±0.05 μm in the single and
0.06±0.02 μm in the multiple group and statistically significant difference was detected (p=0.037). Out of 50 cases, placental hypoxia finding was detected as chorangiosis only in 10 cases (2 multiple, 8 single).
Conclusion: Umbilical artery discordance was detected in cases
with multiple umbilical cord entanglement. However, poor pregnancy outcome was not observed in any of the cases. When multiple
cord entanglement is seen during obstetric examination, umbilical
artery discordance must be remembered and investigated, and also
maternal-fetal condition should be considered.
Keywords: Umbilical cord, umbilical arteries, nuchal cord, discordance.
... [10][11][12] There are studies in the literature which detected the umbilical artery discordance by ultrasonography and/or histopathology, associated it with placental and umbilical cord pathologies, and compared the perinatal outcomes; however, no study was found to examine the discordance in cases with umbilical cord entanglement. [10,[12][13][14] The present study aimed to examine the histopathological diagnosis of the umbilical artery discordance in cases with single or multiple umbilical cord entanglement and its effects on pregnancy outcomes. ...
... [3] Some factors such as Hyrtl's anastomosis and compensation mechanism between arteries may protect against poor obstetrics outcomes; but on the other hand, discordance may accompany fetal abnormalities. [10,[12][13][14] In 14 cases, >1 mm umbilical arteries discordance were detected between 24 and 42 weeks of gestation, but no negative effects on 5-minute Apgar scores of the neonates was observed and explained as discordance being less and was compensated by the functional artery. [13] Similarly, discordance was detected between umbilical arteries (large 1.8±0.3 and small 1. ogy and explained as presence of Hyrtl's anastomosis. ...
... [10,[12][13][14] In 14 cases, >1 mm umbilical arteries discordance were detected between 24 and 42 weeks of gestation, but no negative effects on 5-minute Apgar scores of the neonates was observed and explained as discordance being less and was compensated by the functional artery. [13] Similarly, discordance was detected between umbilical arteries (large 1.8±0.3 and small 1. ogy and explained as presence of Hyrtl's anastomosis. [10] On the other hand, in 12 cases with trisomy 18, intrauterine growth retardation, pulmonary stenosis, maternal diabetes and hypoplastic umbilical artery were detected by ultrasonography. ...
Amaç
Çalışmamızda tek veya çoklu umbilikal kord dolanması olan olgularda umbilikal arter uyumsuzluğuna yönelik histopatolojik tanıyı ve gebelik sonuçlarını incelemeyi amaçladık.
Yöntem
Umbilikal kordun vasküler yapısı, plasentanın histopatolojik bulguları ve obstetrik sonuçlar 50 olguda retrospektif olarak incelendi. Olgular kordon dolanması sayısına (tek-çoklu) göre iki gruba ayrıldı ve olguların histopatolojik bulguları ve neonatal Apgar skorları değerlendirildi.
Bulgular
Elli olgunun 38’inde (%76) tek ve 12’sinde (%24) çoklu kordon dolanması mevcuttu. 50 olgunun ortalama gestasyonel yaşı 39.16±1.06 ve neonatal Apgar skorları 1. dakika için 8.7±0.58, 5. dakika için 9.64±0.56 idi. Gestasyonel yaş (p=0.79), 1. dakika Apgar skoru (p=0.832) ve 5. dakika Apgar skoru (p=0.656) bakımından tekli ve çoklu kordon dolanması gruplarında istatistiksel olarak anlamlı fark yoktu. Histopatolojik muayenede 1. ve 2. umbilikal arterlerin çapı tek kordon dolanması grubunda sırasıyla 0.11±0.12, 0.09±0.05 µm (p=0.756) ve çoklu kordon dolanması grubunda ise sırasıyla 0.13±0.14, 0.06±0.02 µm (p=0.131) olarak bulundu. Umbilikal arteryal çaplar gruba göre karşılaştırıldığında, umbilikal arter 2’nin çapı tek kordon dolanması grubunda 0.09±0.05 µm ve çoklu kordon dolanması grubunda 0.06±0.02 µm olarak bulundu ve istatistiksel olarak anlamlı fark vardı (p=0.037). Elli olgunun 10’unda (2 çoklu, 8 tek) plasental hipoksi bulgusu sadece koranjiozis olarak tespit edildi.
Sonuç
Çoklu umbilikal kord dolanması olan olgularda umbilikal arter uyumsuzluğu tespit ettik, fakat olguların herhangi birinde kötü gebelik sonucu gözlemlemedik. Obstetrik muayenede çoklu kordon dolanması görülmesi halinde, umbilikal arter uyumsuzluğu hatırlanarak araştırılmalı ve ayrıca maternal-fetal durum dikkate alınmalıdır.
Anahtar Kelimeler
Umbilikal kord, umbilikal arterler, nukal kord, uyumsuzluk.
... The allantois duct is lined with a flat monolayer of epithelium [19]. Anastomoses may be formed between the vessels and the course of the vessels forms a spiral, providing great flexibility [20]. The mesoderm of all the ducts running in the umbilical cord fuses together and develops into a mucous connective tissue (tela mucoidea connectens), otherwise known as Wharton's jelly. ...
Mesenchymal stem/stromal cells (MSCs) are currently one of the most extensively researched fields due to their promising opportunity for use in regenerative medicine. There are many sources of MSCs, of which cells of perinatal origin appear to be an invaluable pool. Compared to embryonic stem cells, they are devoid of ethical conflicts because they are derived from tissues surrounding the fetus and can be safely recovered from medical waste after delivery. Additionally, perinatal MSCs exhibit better self-renewal and differentiation properties than those derived from adult tissues. It is important to consider the anatomy of perinatal tissues and the general description of MSCs, including their isolation, differentiation, and characterization of different types of perinatal MSCs from both animals and humans (placenta, umbilical cord, amniotic fluid). Ultimately, signaling pathways are essential to consider regarding the clinical applications of MSCs. It is important to consider the origin of these cells, referring to the anatomical structure of the organs of origin, when describing the general and specific characteristics of the different types of MSCs as well as the pathways involved in differentiation.
... 1 Prenatal sonography of the Hyrtl anastomosis will be discussed in detail following. 2,3 Recent emerging data support that approximately 20% of stillbirth cases can be attributed at autopsy to lethal compromise of umbilical cord circulation. 4-6 Furthermore, precise placental histological criteria accompanying restriction of umbilical cord flow have been established, which enable unique determination of potential umbilical cord compromise, previously unsuspected prior to histological assessment. ...
... 67 Raio et al in 1999 reported two cases of in utero depiction of blood flow within Hyrtl's anastomosis with a pulsatile blood flow from the umbilical artery with a higher resistance index to the umbilical artery with a lower resistance index. 2 This finding was confirmed after delivery, supporting the hypothesis that Hyrtl's anastomosis functions in equalizing blood pressure between the two umbilical arteries and regulating blood pressure within the placental lobes. 2 This same group of investigators in 2001 reported a series of functional evaluations of Hyrtl's anastomosis in 41 women, measuring the resistance index of the anastomosis and the umbilical arteries proximal and distal to the anastomosis. 3 The direction of blood flow within the anastomosis was depicted by color Doppler imaging. ...
... 67 Raio et al in 1999 reported two cases of in utero depiction of blood flow within Hyrtl's anastomosis with a pulsatile blood flow from the umbilical artery with a higher resistance index to the umbilical artery with a lower resistance index. 2 This finding was confirmed after delivery, supporting the hypothesis that Hyrtl's anastomosis functions in equalizing blood pressure between the two umbilical arteries and regulating blood pressure within the placental lobes. 2 This same group of investigators in 2001 reported a series of functional evaluations of Hyrtl's anastomosis in 41 women, measuring the resistance index of the anastomosis and the umbilical arteries proximal and distal to the anastomosis. 3 The direction of blood flow within the anastomosis was depicted by color Doppler imaging. ...
The umbilical cord constitutes a continuation of the fetal cardiovascular system anatomically bridging between the placenta and the fetus. This structure, critical in human development, enables mobility of the developing fetus within the gestational sac in contrast to the placenta, which is anchored to the uterine wall. The umbilical cord is protected by unique, robust anatomical features, which include: length of the umbilical cord, Wharton’s jelly, two umbilical arteries, coiling, and suspension in amniotic fluid. These features all contribute to protect and buffer this essential structure from potential detrimental twisting, shearing, torsion, and compression forces throughout gestation, and specifically during labor and delivery. The arterial components of the umbilical cord are further protected by the presence of Hyrtl’s anastomosis between the two respective umbilical arteries. Abnormalities of the umbilical cord are uncommon yet include excessively long or short cords, hyper or hypocoiling, cysts, single umbilical artery, supernumerary vessels, rarely an absent umbilical cord, stricture, furcate and velamentous insertions (including vasa previa), umbilical vein and arterial thrombosis, umbilical artery aneurysm, hematomas, and tumors (including hemangioma angiomyxoma and teratoma). This commentary will address current perspectives of prenatal sonography of the umbilical cord, including structural anomalies and the potential impact of future imaging technologies.
... 1,2 Many theories have been put forward explaining its function in equalizing the pressure between the two arteries. 1,2,3,4,5,6 The importance of an intact endothelium and recognizing the value of the blood vessel endothelium in the uteroplacental circulation has been greatly increased. Reduction in the uteroplacental blood flow, abnormal placentations are often associated with pregnancy-induced hypertension. ...
BACKGROUND The human umbilical arteries form an important component involved in the exchange of materials between the foetus and the mother. Hypertensive disorders in pregnancy are responsible for a significant amount of maternal and perinatal morbidity and mortality. It complicates about 6 - 20 % of all pregnancies. Although PIH (Pregnancy-induced hypertension) is one of the major causes of maternal death, especially in developing countries; its perinatal outcomes are also not so favourable. We wanted to study the ultrastructure of Hyrtl’s anastomosis between the normotensive and hypertensive placentas. METHODS A cross-sectional study was carried out to assess the variable anatomy in Hyrtl’s anastomosis and determine the alterations of the Hyrtl’s anastomosis in the case of pregnancy-induced hypertension from the year 2017-2018 at Sikkim Manipal Institute of Medical Sciences. For TEM (transmission electron microscopy) the portion of the Hyrtl’s anastomosis was carefully dissected out and processed. The study included women with pregnancy-induced hypertension if their arterial blood pressure with systolic as ≥ 140 mm Hg and diastolic ≥ 90 mm Hg measured on two or more occasions at least after the 20th week of gestation with or without oedema. Due to an inadequate number of cases essential hypertensive cases were excluded. RESULTS From the study conducted, transmission electron microscopy revealed a disrupted muscular layer in pregnancy-induced hypertension when compared to normal Hyrtl’s anastomosis. Thickening of the muscular layer was observed in the pregnancy-induced Hyrtl’s anastomosis. Statistical Analysis - Independent t-test was considered in the analysis for continuous among the ultrastructure of the Hyrtl’s anastomosis between the normotensive and hypertensive groups. P ≤ 0.05 was considered significant. SPSS 20.0 was used for data analysis. CONCLUSIONS The effect of hypertension brought about structural changes in the blood vessel which might probably have an effect on the fetoplacental circulation and therefore adversely affecting the foetal outcome. KEY WORDS Hyrtl’s Anastomosis, Pregnancy- Induced Hypertension
... The presence of the Hyrtl anastomosis has been confirmed in a number of prenatal ultrasound studies. [7][8][9] The "safety valve" protection from potential umbilical artery compression is clearly absent in the presence of a single umbilical artery (the most common true congenital anomaly of humans). 6 It is precisely this loss of protection from potential umbilical artery compromise due to compression in fetuses with a single umbilical artery, which we address in extending the definition of complex umbilical cord entanglement to include any umbilical cord entanglement (nuchal or true knot) in the presence of a single umbilical artery. ...
Diagnosis of potential umbilical cord compromise, namely, true knots of the umbilical cord and nuchal cords has been enabled with increasing accuracy with current enhanced prenatal sonography. Often an incidental finding at delivery, the incidence of true knots of the umbilical cord has been estimated at between 0.04% and 3% of deliveries. This condition has been reported to account for a 4 to 10-fold increase of stillbirth and perinatal morbidity of 11% of cases. Nuchal cords, commonly observed at the delivery of uncompromised, non-hypoxic non-acidotic newborns occur more frequently with single nuchal cords noted in between 20% and 35% of all deliveries at term. Multiple nuchal cords are considerably less frequent, with decreasing frequencies inverse to the number of nuchal cord loops. While clearly single (and likely double) nuchal cords are almost uniformly associated with favorable neonatal outcomes, emerging data suggest that cases of ≥3 loops of nuchal cords are more likely to be associated with an increased risk of adverse perinatal outcome (either stillbirth or compromised neonatal condition at delivery). We define cases of a true knot of the umbilical cord, cases of ≥3 loops of nuchal cords, any combination of a true knot and nuchal cord, or any umbilical cord entanglement (nuchal or true knot) in the presence of a single umbilical artery, in singleton gestations as complex umbilical cord entanglement. Two concurrent developments, the increase in accuracy of prenatal sonographic diagnosis of complex umbilical cord entanglement and recent data confirming fatal compromise of the umbilical circulation in approximately 20% of cases of stillbirth, suggest that establishing governing body guidelines for reporting of potential umbilical cord compromise, and recommendation of consideration for early-term delivery of select cases, may be warranted. This commentary will address current perspectives of prenatal diagnosis and clinical management challenges of complex umbilical cord entanglement.
... 7 This arterial anastomosis equalizes pressures between the respective umbilical arteries before entering the placenta and functions as a safety valve in the event of placental compression or blockage of an umbilical artery, and has been confirmed with prenatal ultrasound. [7][8][9] The important (and possibly critical) safety effect of this anastomosis will be detailed later in conjunction with the (not uncommon) association of a single umbilical artery (the most common true congenital anomaly in humans) and nuchal cord(s). ...
Umbilical cord accidents preceding labor are uncommon. In contrast, nuchal cords are a very common finding at delivery, with reported incidences of a single nuchal cord of approximately between 20% and 35% of all singleton deliveries at term. Multiple loops occur less frequently, with reported incidence rates inverse to the number of nuchal cords involved. Rare cases of up to 10 loops of nuchal cord have been reported. While true knots of the umbilical cord have been associated with a 4–10-fold increased risk of stillbirth, nuchal cord(s) are most often noted at delivery of non-hypoxic non-acidotic newborns, without any evidence of subsequent adverse neonatal outcome. Prior to ultrasound, nuchal cords were suspected clinically following subtle (spontaneous or evoked) electronic fetal heart rate changes. Prenatal sonographic diagnosis, initially limited to real-time gray-scale ultrasound, currently entails additional sonographic modalities, including color Doppler, power Doppler, and three-dimensional sonography, which have enabled increasingly more accurate prenatal sonographic diagnoses of nuchal cord(s). In contrast to true knots of the umbilical cord (which are often missed at sonography, reflecting the inability to visualize the entire umbilical cord, and hence are often incidental findings at delivery), nuchal cord(s), reflecting their well-defined and sonographically accessible anatomical location (the fetal neck), lend themselves with relative ease to prenatal sonographic diagnosis, with increasingly high sensitivity and specificity rates. While current literature supports that single (and possibly double) nuchal cords are not associated with increased adverse perinatal outcome, emerging literature suggests that cases of ≥3 loops of nuchal cords or in the presence of a coexisting true knot of the umbilicus may be associated with an increased risk of stillbirth or compromised neonatal status at delivery. This commentary will address current perspectives of prenatal sonographic diagnosis and clinical management challenges associated with nuchal cord(s) in singleton pregnancies.
... Moreover, near the placental end of the umbilical cord, the interarterial anastomosis, called the Hyrtl anastomosis, is present. Its role includes the alignment of blood pressure between both arteries, as well as the protection of the placenta when artery compression occurs [23]. ...
Stem cell therapies offer a great promise for regenerative and reconstructive medicine, due to their self-renewal and differentiation capacity. Although embryonic stem cells are pluripotent, their utilization involves embryo destruction and is ethically controversial. Therefore, adult tissues that have emerged as an alternative source of stem cells and perinatal tissues, such as the umbilical cord, appear to be particularly attractive. Wharton’s jelly, a gelatinous connective tissue contained in the umbilical cord, is abundant in mesenchymal stem cells (MSCs) that express CD105, CD73, CD90, Oct-4, Sox-2, and Nanog among others, and have the ability to differentiate into osteogenic, adipogenic, chondrogenic, and other lineages. Moreover, Wharton’s jelly-derived MSCs (WJ-MSCs) do not express MHC-II and exhibit immunomodulatory properties, which makes them a good alternative for allogeneic and xenogeneic transplantations in cellular therapies. Therefore, umbilical cord, especially Wharton’s jelly, is a promising source of mesenchymal stem cells.
... Finally, an additional safety mechanism is the presence of a 1.5-2 cm shunt between the umbilical arteries within 3 cm of the placental cord insertion, the Hyrtl anastomosis, which is present in approximately 96% of umbilical cords. 1 This arterial anastomosis equalizes pressures between the respective umbilical arteries before entering the placenta and functions as a safety valve in the event of placental compression or blockage of an umbilical artery. 1 Prenatal sonographic assessment of the Hyrtl anastomosis, has depicted pulsatile unidirectional flow within the Hyrtl anastomosis toward the umbilical artery with lower resistance index, supporting the hypothesis that the Hyrtl anastomosis plays an important function when the placental areas supplied by the umbilical arteries, differ in size. 2,3 An array of umbilical cord abnormalities exists including among others, single umbilical artery, fused umbilical arteries, umbilical cord cysts, umbilical artery aneurysm, four-vessel cords (resulting from the persistence of the right umbilical vein), umbilical vein varix, umbilical vein thrombosis, umbilical cord hemangioma, umbilical cord stricture, and abnormalities of the intra-abdominal fetal umbilical vein. 1,4,5 Despite the previously described protective mechanisms of the umbilical cord, this structurecritical for fetal development, is prone to potential compression and entanglement problems, such as nuchal loops (single or multiple) and the formation of true (and compound) knots ( Figure 1). ...
Umbilical cord accidents preceding labor are rare. Single and multiple nuchal cords, and true knot(s) of the umbilical cord, are often incidental findings noted at delivery of non-hypoxic non-acidotic newborns without any evidence of subsequent adverse neonatal outcome. In contrast to single nuchal cords, true knots of the umbilical cord, which occur in between 0.04% and 3% of all deliveries, have been associated with a reported 4 to 10 fold increased risk of stillbirth. First reported with real-time ultrasound, current widespread application of color Doppler, power Doppler and three-dimension sonography, has enabled increasingly more accurate prenatal sonographic diagnoses of true knot(s) of the umbilical cord. Reflecting the inability to visualize the entire umbilical cord at prenatal ultrasound assessment, despite detailed second and third-trimester scanning, many occurrences of incidental true knot of the umbilical cord remain undetected and are noted only at delivery. Although prenatal sonographic diagnostic accuracy is increasing, false positive sonographic diagnosis of true knot of the umbilical cord cannot be ruled out with certainty, and must continue to be considered clinically. Notwithstanding the inability to diagnose all true knots, currently there is a clear absence of clinical management guidelines by governing bodies regarding patients in whom prenatal sonographic diagnosis of true knot(s) of the umbilical cord is / are suspected. As a result, in many prenatal ultrasound units, suspected sonographic findings suggestive of or consistent with true knot of the umbilical cord are often disregarded, not documented, and patients are not uniformly informed of this potentially life-threatening condition, which carries an associated considerable risk of stillbirth. This commentary will address current perspectives of prenatal sonographic diagnostic and management challenges associated with true knot(s) of the umbilical cord in singleton pregnancies.
... On the contrary, arterial blood is under higher pressures through most of UC, which results in a higher velocity [33]. However, umbilical arterial blood slows down or arterial flow decreases at an only proximal section within 5 cm of the cord insertion site into the placental fetal surface, as it enters the watershed of the chorionic vessel network, where high-capacitance/low-resistance blood is distributed to the chorionic villi [33][34][35]. This blood flow deceleration within this segment of UC is due to the Hyrtl anastomosis, which joins the 2 arteries just before they enter CP, effectively equalizing the pressures between the 2 arteries and contributing to a decreased end diastolic flow [33][34][35]. ...
... However, umbilical arterial blood slows down or arterial flow decreases at an only proximal section within 5 cm of the cord insertion site into the placental fetal surface, as it enters the watershed of the chorionic vessel network, where high-capacitance/low-resistance blood is distributed to the chorionic villi [33][34][35]. This blood flow deceleration within this segment of UC is due to the Hyrtl anastomosis, which joins the 2 arteries just before they enter CP, effectively equalizing the pressures between the 2 arteries and contributing to a decreased end diastolic flow [33][34][35]. This decrease in velocity should allow for more effective neutrophil margination from UA in the proximal portion of UC [33]. ...
OBJECTIVES:No information exists about whether fetal inflammatory-response(FIR), early-onset neonatal sepsis(EONS) and chorioamnionitis(an advanced-stage of maternal inflammatory-response in extraplacental membranes) continuously increase according to the progression of inflammation in umbilical-cord(UC). The objective of current-study is to examine this-issue. METHODS:Study-population included 239singleton pregnant-women(gestational-age[GA] at delivery: 21.6~36weeks) who had inflammation in extraplacental membranes or chorionic plate (CP) and either preterm-labor or preterm-PROM. We examined FIR, and the frequency of fetal inflammatory-responses syndrome(FIRS), proven-EONS, suspected-EONS and chorioamnionitis according to the progression of inflammation in UC. The progression of inflammation in UC was divided with a slight-modification from previously reported-criteria as follows: stage0, inflammation-free UC; stage-1: umbilical phlebitis only; stage-2: involvement of at least one UA and either the other UA or UV without extension into WJ; stage-3: the extension of inflammation into WJ. FIR was gauged by umbilical-cord-plasma(UCP) CRP concentration(ng/ml) at birth, and FIRS was defined as an elevated UCP CRP concentration at birth(≥200ng/ml). RESULTS:Stage-0, stage-1, stage-2 and stage-3 of inflammation in UC were present in 48.1%, 15.5%, 6.7%, and 29.7% of cases. FIR continuously increased according to the progression of inflammation in UC(Kruskal-Wallis test,P
