A true knot occurs when the umbilical cord loops around itself during pregnancy as the fetus moves around in the amniotic fluid. When that knot tightens, it can compress the blood vessels in the umbilical cord, cutting off the supply of oxygen-rich blood to the fetus.
Knotting of the umbilical cord—“true knot of cord”—is a rather rare event (about 1% of term deliveries)  and a challenging antepartum diagnosis .
The occurrence of true knot of the umbilical cord is not rare; however, for such a knot to be pulled tight enough in utero to cause fetal death is a rare occurrence. Cases resulting in fetal death prior to the onset of labor are believed to be especially rare.
How common are cord knots? Umbilical cord knots occur in about one in every hundred pregnancies. (More common than knots are nuchal loops, the technical term for when the cord wraps around a baby’s neck.
An abnormal or non-reassuring fetal heart rate will occur when the knot is serious enough to cause a decrease of oxygen to the baby’s brain. There is nothing a woman can do to prevent a true umbilical cord knot from forming (1). Doctors should monitor the baby closely if there are concerns of decreased fetal activity.
Most knots don’t cause problems for your baby. As long as the knot isn’t too tight, blood flow and nutrients aren’t restricted. However, a tight knot leaves your baby without enough oxygen and puts them at risk for brain damage and even stillbirth.
Prenatal diagnosis of an umbilical cord true knot is difficult through 2D ultrasound, but today, with ultrasound achievement in 3D and Doppler mode is easily possible. True knots should be distinguished from false knots.
A number of factors have been described to increase the predisposition to true umbilical cord. True knots may arise from movements of the fetus in utero. In the early pregnancy, this event is more likely to develop because relatively more amniotic fluid is present and greater fetal movement usually occurs.
A stillbirth is the death of a fetus in the uterus after week 20 of pregnancy. The reasons go unexplained for 1 in 3 cases. The rest may be caused by problems with the placenta or umbilical cord, high blood pressure, infections, birth defects, or lifestyle choices.
True knots get more dangerous the closer a baby gets to birth, and in a worse-case scenario can cause asphyxia, leading to brain damage or death. Tight knots have a mortality rate of 10%.
Among these abnormalities, a cord true knot is very rare, with a probability of occurrence of approximately 0.3%-2%. This occurs when the fetus flips in the amniotic sac and slips through a loop in the umbilical cord. With this in mind, the possibility of formation of two true knots in the birth cord is roughly zero.
Abstract. True knots of the umbilical cord can represent a serious complication for the fetus due to the possible alteration in the fetal circulation with consequent intrauterine growth restriction or fetal death.
The umbilical cord can be visualized throughout most of gesta- tion and is detectable sonographically soon after visualization of the fe- tal pole. The normal umbilical cord is 50-60 cm long and may coil as many as 40 times, usually to the left.
ABSTRACT. True knots of the umbilical cord are complications that can result in obstetric disasters, including fetal asphyxia and eventual fetal death. This study reports on 13 patients with a true knot of the umbilical cord in a delivery population of 967 deliveries during a 1-year period.
Stillbirth affects about 1 in 160 births, and each year about 24,000 babies are stillborn in the United States. That is about the same number of babies that die during the first year of life and it is more than 10 times as many deaths as the number that occur from Sudden Infant Death Syndrome (SIDS).
There’s no way yet to prevent nuchal cords or unwind them from a baby’s neck in the womb. But when a baby is born with a nuchal cord, your doctor will know what to do because it happens so frequently. The colored sections of the ultrasound show that the umbilical cord is under the baby’s chin.
Signs of distress can include increased or decreased movement in the womb, an abnormally fast or abnormally slow heart rate, feeling the umbilical cord physically drop into the cervix, and a measurable size deficiency in the baby based on the average size of a fetus during pregnancy.
About 1 in 100 pregnancies (about 1 percent) have a knot in the umbilical cord. If a knot gets pulled tight, it can cut off your baby’s oxygen. This can cause miscarriage or stillbirth.
Abstract. Background: Amniotic band syndrome with umbilical cord strangulation is extremely rare and is usually described during second trimester. We present a case of umbilical cord strangulation causing fetal demise in a full-term otherwise healthy fetus.
Signs The Umbilical Cord Is Around Baby’s Neck
It’s visible via ultrasound. Your practitioner can detect a nuchal cord about 70 percent of the time during routine ultrasounds, although it’s usually not possible to determine if the cord is short or tight around the neck.
What Causes a Nuchal Cord? The fetal movements your baby makes before they are born is the most common cause of nuchal cords. An extra amount of amniotic fluid, allowing your baby to move around more freely, as well as a longer than average umbilical cord, might also cause your baby to have a nuchal cord.
In fact, 25 to 40% of babies are born with their umbilical cord wrapped around their neck (called a nuchal cord). There is nothing that can be done to prevent this. But, there is no need to worry.
In first-time mothers, dropping usually occurs 2 to 4 weeks before delivery, but it can happen earlier. In women who have already had children, the baby may not drop until labor begins. You may or may not notice a change in the shape of your abdomen after dropping.
Most babies born unexpectedly without a heartbeat can be successfully resuscitated in the delivery room. Of those successfully resuscitated, 48% survive with normal outcome or mild-moderate disability.
The most common symptom of stillbirth is when you stop feeling your baby moving and kicking. Others include cramps, pain or bleeding from the vagina. Call your health care provider right away or go to the emergency room if you have any of these conditions.