Cord entanglement around the fetal neck – causes and consequences24.05.2022
The umbilical cord is a cord that connects the fetus to the mother’s placenta. The umbilical cord contains two umbilical arteries and an umbilical vein. Arteries carry blood with metabolic products enriched with carbon dioxide to the mother’s placenta. Blood containing useful compounds and oxygen enters the fetus through a vein. In some cases, the umbilical cord may be wrapped around the neck of the fetus, which complicates the course of childbirth, and sometimes poses a threat to the life and health of the child. It is worth noting that the compressive effect of the umbilical cord on the neck is not dangerous for the fetus, since breathing through the lungs and upper airways is not carried out in the prenatal period. The danger is the tension of the umbilical cord, leading to placental abruption, and compression of the vessels inside it, leading to acute hypoxia and fetal asphyxia.
True entanglement is when the umbilical cord is located around the neck of the fetus for 360 degrees or more.
The frequency of a single entanglement of the neck of the fetus with the umbilical cord is about 20%, twice – less than 2.9%, three times – 0.6%. The maximum entanglement described in the literature is 9 times. In the event of fetal hypoxia in 50% of cases, the cause is entanglement of the umbilical cord. In 3% of cases, pathology is the cause of the death of a child during childbirth.
Reasons for entanglement
The cause of entanglement is most often a long umbilical cord. Normally, the length of the umbilical cord is 50–70 cm. With a length of the umbilical cord of more than 80 cm, the probability of pathology increases several times.
Another reason is chronic fetal hypoxia, which is usually observed in smoking mothers.
Nicotine contained in cigarettes contributes to the narrowing of the vessels of the placenta and fetus, disruption of the fetoplacental blood flow. The fetus does not receive enough oxygen, stress hormones – adrenaline and cortisol – begin to be released into the blood, which leads to restless chaotic movements of the baby and contributes to the entanglement of the umbilical cord around the torso and neck. Chronic fetal hypoxia can also occur with some maternal diseases, such as diabetes mellitus, thrombophilia, preeclampsia, and hypertension.
Predisposing factors are polyhydramnios and frequent stress in the mother. Stress hormones penetrate the umbilical cord into the blood of the fetus, as a result, the child becomes more mobile, in the presence of polyhydramnios it can confuse the umbilical cord.
Common myths about the occurrence of entanglement, when the mother does gymnastics or homework with a raise of her hands, knits, have no justification.
Cord entanglement classification:
- neck wrap:
- incomplete (less than 360 degrees);
- entanglement of the body;
- entanglement of limbs;
- combined entanglement (several areas).
Symptoms of cord entanglement
During pregnancy, cord entanglement usually does not give a clinical picture. Changes in the state of the fetus occur during childbirth. With a single entanglement, childbirth usually proceeds favorably and without complications. Perhaps a short-term increase in the fetal heart rate in the second stage of labor (during attempts), when the eruption of the head occurs.
With repeated entanglement, acute fetal hypoxia (lack of oxygen) may occur. It occurs due to the relative shortening of the umbilical cord. There is a pronounced tension of the umbilical cord, narrowing of the lumen of the blood vessels, there is an acute lack of oxygen. This condition threatens the life of the fetus. The risk increases when the entanglement is combined with other pathologies (oligohydramnios, skinny and non-tortuated umbilical cord, the presence of a true umbilical cord knot).
One of the complications during childbirth due to excessive tension of the umbilical cord can be premature detachment of the placenta.
In the absence of pathology, the placenta separates from the uterus some time after the birth of the child. When entangled, a relative shortening of the umbilical cord occurs, it stretches, and traction of the placenta occurs. During one of the attempts, placental abruption may occur, which leads to acute hypoxia of the fetus and its death.
If repeated entanglement of the umbilical cord around the neck persists during childbirth, extensor positions of the fetal head may occur. Normally, the fetus passes through the birth canal with the back of the head, that is, the minimum size of the head circumference. At the same time, his head assumes a moderately flexed position. Loops of the umbilical cord on the fetal neck prevent this bending. As a result, the child passes through the birth canal with the crown, forehead or face, which contributes to the occurrence of injuries in the mother (ruptures of the cervix, vagina, perineum) and damage to the cervical spine in the child.
Diagnosis of cord entanglement
History taking is of great importance. The likelihood of developing umbilical cord pathology increases if entanglement has already been observed in a previous pregnancy.
The main diagnostic method is an ultrasound examination performed after the 12th week of pregnancy. Most often, the entanglement is detected on the third mandatory ultrasound (at the 32nd week of gestation). The doctor assesses the presence of entanglement, determines whether it is complete or not, the number of turns, tight or loose. A single loose entanglement often disappears before childbirth.
To determine the multiplicity of entanglement, dopplerometry is performed, in which the blood flow of the fetus and placenta is visualized.
Doppler color mapping is also performed in difficult diagnostic cases, when it is not possible to say for sure by ultrasound whether there is an entanglement or umbilical cord loops are simply located next to the fetal neck.
Chronic hypoxia of the fetus may be an indirect sign of the presence of entanglement. After the 32nd week of pregnancy (and according to indications even earlier), cardiotocography (CTG) is performed. During CTG, fetal movements are counted and the heart rate is determined. With hypoxia during CTG, frequent episodes of a decrease in heart rate are determined.
It is impossible to unravel the loops of the umbilical cord in the fetus in the prenatal period. Treatment consists in strict control over the condition of the fetus, prevention of placental insufficiency and hypoxia, determination of the optimal time and method of delivery.
If there is a single entanglement of the umbilical cord, no additional measures are taken. With a double entanglement, a woman is recommended to perform cardiotocography (CTG) every 7-10 days. CTG allows you to determine fetal hypoxia in time and take appropriate measures. Multiple entanglement is an indication for antenatal hospitalization in the department of pregnancy pathology for intensive daily monitoring of the fetus, timing and determining the method of delivery. If there is chronic fetal hypoxia, special drugs may be prescribed to protect the nervous system from damage and improve blood flow. With the development of acute fetal hypoxia, an emergency caesarean section is performed, regardless of the gestational age. In other cases, the timing of delivery depends on the condition of the fetus, the presence of complications (for example, fetal growth retardation in chronic hypoxia).
During childbirth, if there is entanglement of the umbilical cord, CTG is performed every 30 minutes during contractions and after each attempt.
In the case when the heart rate goes beyond the norm in the first stage of labor (during labor), an emergency caesarean section is performed (with a slight dilatation of the cervix) or stimulation with oxytocin (with an opening of more than 8 cm). If violations are detected in the second period (during attempts), an episiotomy (perineal dissection) is used. After the birth of the head, the doctor’s task is to free the baby’s neck from the loops of the umbilical cord in order to prevent tension and disruption of blood flow.
Forecast and prevention
The fear of the umbilical cord entwining around the neck of the fetus is greatly exaggerated. A single non-tight entanglement develops in childbirth in 30% of women and does not affect labor and the health of the child.
A single entanglement in the absence of other pathology is not an indication for a caesarean section.
Prevention of entanglement consists in the prevention of fetal hypoxia. A pregnant woman should follow the regimen, avoid stress, stop smoking, spend more time outdoors. According to the indications, the doctor may prescribe drugs that improve uteroplacental blood flow.