The incidence of a true knot in the umbilical cord is about one out of one hundred pregnancies. There are certain situations where the incidence of a knot in the cord is increased. These conditions include polyhydramnios (unusually large amount of amniotic fluid), male fetuses, long umbilical cords, twins, and a patient with previous deliveries.
The diagnosis of a true knot is usually made at the time of delivery. Ultrasound can also detect a true knot in the cord, but is often missed.
Labor is usually monitored by intermittent or continuous auscultation of the infant’s heart rate. As the infant descends into the birth canal, the knot will often tighten which will decrease the amount of oxygen that the infant is receiving. As a consequence, the fetal heart rate will slow. This is often the first clue that an umbilical cord knot may exist. Depending on the severity of the fetal heart rate decrease, your provider may elect to perform a cesarean section.
If a knot is diagnosed prior to labor, your provider may elect to attempt a vaginal delivery. If this is the case, your infant’s heart rate will be followed very closely for any signs of fetal compromise. On the other hand, the provider may elect to perform an elective cesarean section. What mode of delivery is ultimately chosen will depend on the conversation that he will have with you prior to labor where he will delineate the risks and benefits of a trial of labor versus an elective cesarean section. If you both elect to proceed with a cesarean section, he will explain the risks of surgery as infection, hemorrhage, injury to another organ system, and/or death.
Rarely, the umbilical cord knot may cause an intrauterine fetal demise (stillborn) prior to the onset of labor. If the provider is aware that your infant has an umbilical cord with a true knot, he may elect to perform weekly or twice weekly nonstress tests (NST) and a weekly biophysical profile (BPP) until the infant is born. Both the NST and the BPP are tests of fetal well being, and help to reassure your provider that the infant is doing well.
The present recommendation by the American College of Obstetricians and Gynecologists (ACOG) is to deliver an infant no sooner than 39 weeks gestation. Depending on the NST and BPP, however, your provider may suggest that you deliver earlier than the recommended 39 weeks gestation. He may also recommend an early delivery if there is decreased fetal movement. You may also be advised to follow kick counts in the event of decreased fetal movement. Kick counts is a technique where you note the number of the infant’s kicking in a certain amount of time.
During my career in obstetrics, I saw several infants with true knots in the umbilical cord. None of these infants had an adverse outcome, and I mentioned earlier, the diagnosis was made at the time of delivery. Some of the infants were delivered vaginally, and others were delivered by cesarean section. I have seen as many as three true knots in the umbilical cord, and I have seen a few with two knots. Again, all these infants did well. There are instances, however, where the infant will perish prior to labor.
It is extremely important that you thoroughly discuss the options of vaginal delivery versus cesarean section with your provider in the event of a diagnosis of a true knot in the umbilical cord. It is also vitally important that you inform your provider of any decreased fetal movement.
Wishing you a memorable and problem free delivery, Pablo.