“Most of the time, a knot in the umbilical cord is a benign thing,” says Pietro Bortoletto, MD, MSc, a reproductive endocrinologist and director of reproductive surgery at Boston IVF. “Some people even think that it is good luck to have a knot in the cord. In rare cases, however, a true knot can be associated with third trimester decreased fetal movement.” To help alleviate some of the concern about a true knot in your baby’s cord, we talked to experts in the field to get the facts about what a true knot is, how it forms, and what risks it poses. Read on to learn more.
What Parents Need to Know About True Knots
Just as the name implies, a true knot is an actual knot in the umbilical cord, much like a knotted shoelace, says Stuart Jones, MD, FACOG, an OB/GYN and attending physician at Avina Women’s Care. And while it may sound like a scary occurrence, it is very rare, occurring in less than 1% of births. Fortunately, the umbilical cord is built to prevent true knots from forming. Wharton’s jelly—a gelatinous substance designed to protect the cord—provides defensive cushioning around the blood vessels of the cord, even if it does get knotted, says Michael Cackovic, MD, a maternal fetal medicine physician and clinical associate professor of obstetrics and gynecology at Ohio State Wexner Medical Center. If a true knot does form, it is likely loosely tied and unlikely to cause any complications, Dr. Jones adds. “Most of time, a true knot only becomes apparent at the time of delivery and doesn’t cause any issue whatsoever. Occasionally during labor, a true knot will cause a deceleration of the fetal heart rate, but that is rare.”
How a True Knot Differs From Other Types of Knots
Different types of knots in the umbilical cord can form during pregnancy and labor as your baby moves within the amniotic fluid, says Dr. Cackovic. For instance, “pseudoknots,” or false knots, are bulges or protuberance in the baby’s umbilical cord that appear to be knots but aren’t. “These false knots are not associated with complications,” points out says Katherine S. Kohari, MD, FACOG, maternal-fetal medicine specialist and assistant professor at Yale School of Medicine.
How True Knots Occur
Exactly how and when umbilical cords become knotted is a matter of debate. Some researchers believe that the knot develops due to increased amniotic fluid and small fetal size, while others believe it occurs primarily during labor. What’s more, even with the latest advancements, ultrasounds of true knots are mostly only recognized postpartum. “No one knows for certain what causes true knots, but [they] are likely to form secondary to fetal movement early in the pregnancy when the baby is small enough to make large flips and turns,” says Dr. Kohari. There also may be some predisposing factors to a knot’s development, says Dr. Cackovic. Some of these factors include long umbilical cords, increased amniotic fluid volume, small size fetuses, male fetuses, gestational diabetes mellitus, monoamniotic twins, and multiparity. That said, a true knot should not be something that causes anxiety, says Dr. Jones. “It is something that occurs so infrequently that it should not be a high concern. Pregnant people have enough on their minds that they should not be worrying about the possibility of a true knot.” Additionally, he points out that there is nothing parents can do to prevent umbilical cord knots from forming. The most important thing you can do is keep an eye on your baby’s movements. “If at any time after 26 to 28 weeks there are decreased fetal movements or it takes longer to get fetal movements in a day, you should call your physician,” he advises.
Diagnosis of a True Knot
There are no direct signs or symptoms of a true umbilical cord knot, and most remain undiagnosed throughout pregnancy—especially because they are very difficult to see on an ultrasound, says Dr. Bortoletto. Instead, most knots are diagnosed at birth. “Diagnosing a true knot is challenging because of the constant movement of the umbilical cord and the presence of loops and other configurations that can give a false impression of a knot,” Dr. Kohari adds. “There also are no treatment options and no way to undo it. Because of this—and the fact that most pregnancies with true knots do well—this is not something that is routinely screened for on ultrasound.” What’s more, as long as the knot remains loose, it won’t cause harm to your baby, adds Dr. Cackovic. If for some reason, the knot becomes tight, it could interfere with the blood flow from the placenta to the baby and cause an oxygen deprivation. But such a complication is most likely to occur during your baby’s descent through the birth canal, he says. “These cases are rare, though, as the Wharton’s jelly works to allow blood to flow freely through the cord,” Dr. Cackovic says.
Potential Risks and Challenges
There is some controversy surrounding the risks posed by a true knot. Some studies show an association with intrauterine fetal demise (IUFD), meconium-stained amniotic fluid (MSAF), and low Apgar scores, while other studies have failed to establish any clinical significance. Researchers speculate that these differences in outcomes might be explained by the level of tightness of the knot and the protection provided by Wharton’s jelly. “The presence of a true knot may result in increased fetal heart rate abnormalities in labor, which may result in the need for a cesarean delivery,” says Dr. Kohari. “However, most pregnancies with umbilical cord knots do not result in cesarean delivery.” There also is an increased risk for stillbirth in pregnancies with true umbilical cord knots, she adds. Consequently, if there is a suspected true knot, providers will watch these pregnancies closely with frequent ultrasounds and fetal testing. But, they may still deliver vaginally. “[In fact,] a trial of labor and vaginal delivery is preferred even if a true knot is detected prenatally on ultrasound as it is impossible to predict if the knot will tighten so much as to cause harm to the baby,” Dr. Cackovic explains.
A Word From Verywell
Although the idea of a true knot in the umbilical cord may sound scary, these abnormalities are not very common. And, when they do occur, they usually do not pose a threat to your baby. In fact, most cords are not detected until after your baby is born. It is also important to remember that if a true knot does occur, you didn’t do anything to cause it. There also is nothing you can do to prevent one from forming. Instead of worrying about the possibility of a true knot, focus on taking care of yourself and paying attention to your baby’s movements and kick counts. Before you know it, you will be welcoming your little one into the world. If you have further worries or concerns about your baby’s development, be sure to reach out to your OB/GYN or healthcare provider with questions.
