I. What is umbilical cord around the neck? The umbilical cord wrapped around the neck of the fetus is called umbilical cord bypass, which means that the umbilical cord is wrapped around the neck of the fetus by 360°. In addition to wrapping around the neck, it may also be wrapped around the baby’s torso, limbs and feet, which is a common phenomenon during labor and delivery. II. Classification of umbilical cord bypass 1. 1 week or more around; 2. Loose or tight (i.e. tight pressure on the fetal neck) III. Why does umbilical cord bypass occur? Umbilical cord wrapping appears to be a random event and is more likely to occur in overactive fetuses and/or fetuses with long umbilical cords. What is the incidence of umbilical cord bypass? 1. Incidence of umbilical cord bypass and week of gestation: generally increases with gestational age. The incidence of umbilical cord bypass in late pregnancy is 15%-34%. 2. Weeks and incidence of umbilical cord bypass: 1 week of umbilical cord bypass is more common than multiple weeks of umbilical cord bypass (11%-28% vs 2%-7%). One study reported that the incidence of umbilical cord bypass at 1, 2, 3 and 4 weeks of labor was 10.6%, 2.5%, 0.5% and 0.1%, respectively. 3, the umbilical cord around the neck and the mother’s age, race and the number of births does not seem to have a relationship. V. NATURAL COURSE Cord bypass may persist or be loosened, and may reoccur after loosening. Although the formation and release of umbilical cord wrapping appears to be a random event, it is more likely to persist at full term and with multiple weeks of wrapping. VI.POSSIBLE SEQUELARIES 1. There is substantial evidence from observational studies that umbilical cord entanglement does not significantly increase the incidence of any clinically significant fetal/neonatal adverse events. 2. Case reports and a number of small case series have shown that umbilical cord bypass is associated with stillbirth, fetal growth restriction, amniotic fluid meconium contamination, and perinatal arterial ischemic stroke, and may increase the incidence of abnormal fetal heart rate at delivery, assisted delivery, low 5-minute Apgar score, and umbilical arterial acidemia. 3. An increased risk of long-term neurodevelopmental abnormalities has been reported. Possible mechanisms of fetal asphyxia caused by umbilical cord around the neck 1. It is possible that the umbilical cord is tightly wrapped around the neck resulting in obstruction of blood flow to the carotid arteries. 2. Compression of the jugular vein may also lead to fetal asphyxia and death. 3. When the umbilical cord tightly compresses itself or the fetal neck, the umbilical vessels are compressed, especially the thin-walled umbilical veins. Eight, the umbilical cord around the neck of the impact on the course of labor 1, labor fetal heart rate: compared with the pregnancy without umbilical cord around the neck, the incidence of abnormal fetal heart rate graphic 60% -80% higher, but the rate of cesarean section did not increase. Induction of labor is higher in pregnancies with umbilical cord bypass; umbilical cord bypass increases, at least somewhat, the incidence of abnormal fetal heart rate. Multi-weekly umbilical cord bypass appears to increase the risk of abnormal fetal heart rate patterns. 2. Umbilical cord wrapping was associated with increased fetal cerebral blood volume during contractions, with no significant effect on cerebral oxygenation or neonatal outcome. The study also found an increased incidence of fetal heart rate variability deceleration. The authors of the study hypothesized that these manifestations resulted from transient compression of the fetal jugular vein by the umbilical cord during contractions. 3. A tight umbilical cord around the neck is a key factor in increasing the risk of adverse outcomes, as a tight umbilical cord can lead to prolonged hypoxemia and acidosis. Management of pregnancy with umbilical cord around the neck 1. Antenatal: In the case of incidental detection of umbilical cord around the neck by ultrasonography, there is no need to change the antenatal workup because of the lack of evidence of a clinically meaningful increase in adverse pregnancy outcomes. 2. During labor: Cord circumduction does not affect our labor management. As the fetal head descends or rotates, the tightness of the umbilical cord around the neck may change and may result in deceleration of the fetal heart rate, which is managed in the same way as any other deceleration of the fetal heart rate at the time of labor. 3. Delivery: If a loosely wrapped umbilical cord is touched after delivery of the fetal head, the cord can usually be loosened by sliding it over the fetal head. If the umbilical cord is too tight to slide over the fetal head, the umbilical cord can be slid backward over the fetal shoulder to deliver the fetus through the umbilical cord loop.