A constricted umbilical ring in a case of a hyper coiled cord at mid gestation resulting in fetal death: No abnor malities were found in the stillborn baby, except for umbilical ring constriction 

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... uterine segment, without a diagnosis of vasa previa, strong associations with variable decelerations, a non-reassuring fetal status, emergency cesarean section and other perinatal complications have been reported. 7 Risk factors for vasa previa include an ultrasound diagnosis of low-lying placenta or placenta previa at an early stage of gestation, a bilobed or succenturiate placenta, 8-10 multiple gestation, 10 suspicion of aberrant vessels, 10,11 cord insertion into the lower uterine segment 11 and an in vivo fertilization pregnancy. 8 The rate of velamentous insertion ranges from 0.5 to 1.69% of singleton pregnancies; this rate is 10-fold higher in multiple pregnancies. 2,3 Vasa previa was previously believed to be very rare, with an estimated occurrence of approximately 1 in every 2,000 to 5,000 pregnancies in older studies. 12 However, the rate of vasa previa (1:365) was found to be much higher in our consecutive series of patients assessed using ultrasound starting in the first trimester. 13 Furthermore, the number of cases of vasa previa is increasing, as recent advances in ultrasonographic screening have enabled clinicians to detect potential cases of vasa previa more precisely. In the past, it was difficult to correctly diagnose vasa previa after delivery, and some patients treated with cesarean section due to indications of a low-lying placenta or who delivered infants with velamentous cord insertion diagnosed after delivery may not have been included in the population counts in previous studies. The intrapartum clinical diagnosis of umbilical cord abnormalities is rare. 14 Since, the ability to visualize the site of placental cord insertion becomes more difficult with advancing gestation, the site should be evaluated in the mid trimester period. 15-17 The criteria for the ultrasound diagnosis of velamentous cord insertion are as follows: the umbilical vessels enter the placental margin parallel to the uterine wall and connect to the superficial placental vessels (Fig. 3); the cord insertion site and velamentous vessels are immobile, even when the uterus is shaken, and the umbilical vessels diverge as they traverse the membrane (Figs 4 and 5). The diagnosis of abnormal cord insertion should be made before delivery, as the relationship between the site of insertion and the location of the placenta within the uterus is consistent after the mid gestation period. 18 With respect to the detection of vasa previa, previous studies have found routine screening of all pregnant females to not be feasible, 19 although transvaginal scanning and color flow Doppler sonography of the cervical region should be employed in patients considered to be at increased risk. 8,9,19 Importantly, our previous study suggested that ultrasonographic detection of the site of placental cord insertion, focusing on the potential for velamentous vessels and cord insertion in the lower uterine segment, enables physicians to effectively detect vasa previa 11 (Figs 6A and B). Furthermore, we previously demonstrated 20,21 umbilical cord insertion in the lower uterine segment in the first trimester to be associated with various placental abnormalities at delivery, including velamentous cord insertion, vasa previa, low-lying placenta, abruption of the placenta, umbilical cord prolapse and abnormal placental forms (Fig. 7). These placental abnormalities are similar to risk factors for vasa previa. Because the early placenta develops in association with advancing gestation in order to ensure an adequate blood supply from more richly vascularized areas in the direction of the uterine body, velamentous cord insertion is frequently observed in cases of umbilical cord insertion in the lower uterine segment during the first trimester. Interestingly, a total of 45% of cases of velamentous cord insertion develop in patients with low cord insertion. 21 Therefore, systematically identifying the site of cord insertion at the time of early screening for fetal abnormalities is a very simple and useful method for detecting vasa previa and velamentous cord insertion as well as various placental and umbilical cord abnormalities. A coiled umbilical cord with support provided by Wharton’s jelly is thought to be more resistant to torsion, stretching and compression. 22 However, several studies have shown that the presence of a hypercoiled cord correlates with poor perinatal outcomes, such as a low- birth weight, meconium staining of the amniotic fluid at birth and fetal growth restriction 23-28 (Fig. 8). The postnatal umbilical coiling index (UCI) is calculated in order to evaluate the degree of umbilical coiling by dividing the total number of coils by the length of the cord in centimeters after delivery. The diagnosis of a hypercoiled cord after delivery is made in cases involving a postnatal UCI of >0.3 coils/cm. 27 Narrow and weak cords near the fetal side are frequently observed in cases of intrauterine fetal death associated with a hypercoiled cord (Fig. 9). It is though that the umbilical cord is weakest on the fetal side and that conditions of a severe hypercoiled cord are associated with sudden fetal death. Alternatively, hypercoiled cords are frequently observed in fetuses exhibiting growth restriction due to the retention of an umbilical blood flow as a result of strong coiling. The antenatal umbilical coiling index (aUCI) is ultrasoni cally calculated by measuring the distance between two adjacent coils of the umbilical artery from the right outer surface of the vascular wall to the next twist (antenatal UCI = 1/distance in centimeters), as proposed by Degani et al 22 (Fig. 10). It is known that the antenatal UCI value is higher than the postnatal UCI value (0.44 ± 0.11 vs 0.28 ± 0.08; p < 0.001). 22 In addition, the 90th percentile, mean and 10th percentile antenatal UCI values in the second trimester have been reported to be 0.602, 0.403 and 0.204 respectively. 24 It has also been demonstrated that the antenatal UCI decreases as the pregnancy progresses to the third trimester due to elongation of the umbilical cord. 29 Therefore, a hypercoiled cord is usually diagnosed in cases in which the antenatal UCI is above 0.6 (Fig. 11). However, only a few fetuses whose umbilical cord is diagnosed as hypercoiled antenatally are compromised during pregnancy or delivery. Although there are various reports of a hypercoiled cord being associated with the umbilical blood flow, 30-32 it remains unclear whether ultrasound screening is needed in such cases, as there is no predictable method of preventing a nonreassuring fetal status or intrauterine fetal death. Skulstad et al 33-35 recently showed that the blood velocity is higher in the umbilical vein at the site of the abdominal ring than in the cord. However, since measure ments of the vessel diameter at the umbilical ring are too small to be valid, the detection of a high venous blood velocity is a superior marker of vascular constriction at the umbilical ring than direct diameter measurements. Furthermore, we previously demonstrated 36 that the venous velocity at the umbilical ring is significantly higher in fetuses with umbilical venous pulsation than in those without this feature. Therefore, there is a signi ficant correlation between the venous velocity and the amplitude of pulsation. In fact, we experienced a case of intrauterine fetal death due to umbilical constriction in association with a hypercoiled cord in which the umbi lical venous flow increased in correlation with the progression of deep umbilical venous pulsation before death. 36 However, to date, there is no way to rescue such fetuses, as the unfavorable conditions resulting from a hypercoiled cord often occur in the early second trimester. Nuchal cords are most frequently seen in cases involv ing umbi lical cord abnormalities, with a prevalence of 15 to 24% at delivery. 37,38 Although the presence of a single nuchal cord does not appear to affect clinical management, patients with multiple nuchal cord entangle ment are more likely to exhibit an abnormal fetal heart rate pattern during advanced labor, an umbilical artery pH of 7.10, require low or mid-forceps application and give birth to an infant with meconium and/or a low 1 minute Apgar score compared with those with single or no cord entanglement. 39 Nuchal cords are usually visualized ultrasonically as dimples with umbilical cords at the neck of the fetus on the sagittal view (Figs 12A and B). Such cases are identified by presence of the cord in the transverse and sagittal plane of the neck lying around at least three of the four sides of the neck. Although there is a linear increase in the incidence of single and multiple loops over the period of gestation, 40-42 nuchal cords continue to appear and disappear over time. 42 However, the difficulty encountered in visualizing the nuchal cord at term and prior to the induction of labor may be due to fetal crowding, the low position of the fetal head and/or a reduced amniotic fluid volume. 43 Generally, the sensitivity of diagnosis is higher for color Doppler imaging, which may have a particular advantage in the presence of ruptured membranes. 43 Although the incidence of umbilical cord prolapse is extremely rare, ranging from 0.12 to 0.62%, 44-47 cases of umbilical cord prolapse are strongly associated with poor neonatal outcomes, including intrauterine fetal death, neonatal death and cerebral palsy, as this condition may cause the cord to be compressed between the fetus and the maternal bony pelvis and/or soft-tissue, leading to fetal hypoxia. 48 Due to the increasing trend to deliver breech babies and cases of multiple pregnancies via cesarean section, the frequency of umbilical cord prolapse has decreased, with a reported incidence of 0.6% in 1932, 0.2% in the 1990s 49 and 0.12 in 2003. 44 Fore-lying of the umbilical cord is diagnosed in cases in which the fetal membrane is intact and the umbilical cord precedes the presenting ...