True umbilical knot (TUK), although not a commonly encountered pathology, hasan important psychological burden on the mother and obstetrician. It has an extremely low prenatal ultrasound diagnosis rate, despite its adverse perinatal outcomes when unknown. We conducted a retrospective observational analytical study on a 7-year period (2015-2021), including all pregnancies overseen by a single fetal-maternal medicine specialist for monitoring and delivery. We analyzed the prenatal detection rate and correlations between prenatal diagnosis of TUK and pregnancy outcome in terms of associated maternal and fetal factors, time and mode of delivery, fetal weight at birth, maternal level of stress, and iatrogenic prematurity. We compared our results with an electronic search of the literature to study the relationship between TUK and prematurity. We prenatally diagnosed 16 TUKs, and there were two false positives and two undiagnosed knots. All of those women had birth at term. The main finding of the review was a small number of studies that included enough cases for analysis. The prematurity rate due to TUK is 14.2%, significantly increased compared to the general population. An umbilical artery flow velocimetry notch in twin pregnancies complicated by TUK was an important ultrasonographic finding. We consider intrauterine fetal death exceptional, and the main adverse neonatal outcome is due to iatrogenic prematurity caused by maternal anxiety of knowing the prenatal diagnosis and mode of delivery. The elective method for diagnosis should be the second-trimester ultrasound scan using three-dimensional (3D) reconstruction and cesarean delivery for a good neonatal outcome. Pregnant women should be counseled to understand the implications of iatrogenic prematurity, especially respiratory distress syndrome, to ensure these infants are delivered at term.
Keywords: 3D-HD Flow Color Doppler; intrauterine fetal death; premature birth; prenatal diagnosis; true umbilical knot; umbilical cord.