Knots of the Umbilical Cord: Incidence, Diagnosis, and Management

( Int J Gynecol Obstet. 2024;00:1–8. doi: 10.1002/ijgo.15373) The umbilical cord is surrounded by Wharton jelly and is frequently referred to as the “lifeline” because of its essential function in transporting nutrients and expelling fetal waste. Factors such as the length and coiling of the cord impact its health and functionality. An essential aspect of umbilical cord function is an arterial anastomosis, known as “Hyrtl anastomosis,” which helps regulate and distribute blood flow to the placenta. This structure, typically located 3 cm before the cord enters the placenta, is vital for fetal well-being, and abnormalities can increase fetal stress or, in severe cases, lead to fetal demise. Umbilical cord knots (UCK) are among the observed abnormalities, often detected accidentally during routine sonography. True knots range from 0.3% to 2.1%, and while usually solitary, multiple knots can occur. Such knots have also been observed in monkey fetuses. The clinical significance of a knot depends on whether it is tight or loose; a tight knot, especially in a hyper-coiled cord, is less flexible and more prone to complications during birth.