Antenatal Detection of True Knot in the Umbilical Cord - How Accurate Can We Be?

Umbilical cord knot (UCK) is associated with increased risk of fetal death, but is usually diagnosed only after delivery. Our objective was to examine the accuracy of prenatal ultrasound in the diagnosis of UCK and the outcomes of these pregnancies.

A prospective study was performed on 56 patients in which UCK was suspected during a routine level-II anatomical scan (study group). Data included demographics, pregnancy outcome, and short-term neonatal follow-up. The control group included pregnant women with normal pregnancy without UCK in a 4:1 ratio matched for gestational age at delivery.

True knot was observed postnatally in 54 out of 56 fetuses (detection rate of 96.4 %). Gestational age at diagnosis of UCK was 22.1 ± 3.1 weeks. The female to male ratio was 1:1 in both groups. Maternal age and parity were significantly higher in pregnancies with UCK compared to controls. The mean gestational age at delivery was 37.1 weeks of gestation in the UCK group. There was no difference in the birthweight percentile. 47 patients (87 %) underwent induction of labor. There were no differences in the rate of cesarean section or Apgar scores. No neonate with UCK needed ventilation. None suffered from seizures and none needed brain imaging. There were no cases of fetal or neonatal death in the pregnancies with UCK.

There is a high detection rate of UCK during targeted scan of the umbilical cord performed during the level-II anatomical scan. Careful pregnancy follow-up and early term delivery may result in excellent obstetrical outcomes.