Umbilical Cord Knots: Is the Number Related to Fetal Risk?

Abstract

True knots of the umbilical cord (UC) are a rare occurrence and are reported in 0.4–1.2% of deliveries. The compression of true knot of the UC can cause obstruction of the fetal circulation, leading to intra-uterine growth retardation or fetal death. Predisposing factors for the genesis of the true UC knot are numerous and include all the conditions, which lead to a relatively large uterine volume. This situation may predispose to free and excessive fetal movements. Although not all true knots lead to perinatal complications, they have been associated with adverse pregnancy outcomes, including fetal distress, fetal hypoxia, intra-uterine growth restriction (IUGR), long-term neurological damage, caesarean delivery and stillbirth. We present a rare case of operative delivery with vacuum in a multiparous woman at term of pregnancy with a double true knot of the UC. As in most cases, the diagnosis was made after delivery, as there were no fetal symptoms during pregnancy. Some authors assume that 3D power sonography may be useful in the diagnosis of true UC knots. However, 3D power Doppler cannot be considered as a definitive method. There are no specific prenatal indications to induce the physician to look for ultrasound signs suggestive of umbilical true knot. Some studies argue that cases of fetal death and fetal risk are directly related to the number of knots. We also support this thesis, even if further observational and retrospective studies are needed to demonstrate it.

Risk Factors of Umbilical Cord Pathology and Factors of Negative Perinatal Consequences and Newborn Incidence

“…This structure is critical to human development, it ensures fetal mobility within the gestational sac and is protected by unique, reliable anatomical features including the length of the umbilical cord, Wharton's jelly, two umbilical arteries, coagulation, and suspension in amniotic fluid [9]. All of these functions contribute to the protection and buffering of this important structure from potentially harmful forces of coiling, shifting and compression during pregnancy, especially during labour [10][11][12][13]. In scientific sources, there are informative reports indicating a strong association between the diameter of the umbilical cord and the weight of the placenta and the weight of the newborn [14][15][16]; the connection with oligohydroamnion, fetal distress, delayed fetal development, perinatal mortality and morbidity has also been proven [1,4,[17][18][19].…”

A misdiagnosed case of a 150-cm umbilical cord coiled twice around the fetal neck with a true cord knot: A rare Syrian case report

“… 13 Knots can cause either severe outcomes or benign due to their level of tightness just like nuchal loops. 14 A rare but classic radiological finding used to diagnose a true knot is the “hanging noose sign,” and it shows a cross-section of the UC surrounded by one of the UC loops. 15 Maybe this sign was interpreted as a malformation by the private doctor in our case.…”

Umbilical Cord Diseases Affecting Obstetric and Perinatal Outcomes

“…It significantly increases the rate of stillbirth, with an odds ratio (OR) of 3.96 [18], and it can be associated with adverse perinatal outcomes such as IUGR, preterm birth, low Apgar scores, and stillbirth [25,26]. True knots have been reported to lead to a four-fold increase in IUFD due to vascular compression as long as the knot tightens [27]. They are more common in mothers with an advanced age, multiparity, previous miscarriages, polyhydramnios, and diabetes [18,26].…”