Abstract
Umbilical cord abnormalities are not rare, and are often associated with structural or chromosomal abnormalities, fetal intrauterine growth restriction, and poor pregnancy outcomes; the latter can be a result of prematurity, placentation deficiency or, implicitly, an increased index of cesarean delivery due to the presence of fetal distress, higher admission to neonatal intensive care, and increased prenatal mortality rates. Even if the incidence of velamentous insertion, vasa praevia and umbilical knots is low, these pathologies increase the fetal morbidity and mortality prenatally and intrapartum. There is a vast heterogeneity among societies’ guidelines regarding the umbilical cord examination. We consider the mandatory introduction of placental cord insertion examination in the first and second trimester to practice guidelines for fetal ultrasound scans. Moreover, during the mid-trimester scan, we recommend a transvaginal ultrasound and color Doppler assessment of the internal cervical os for low-lying placentas, marginal or velamentous cord insertion, and the evaluation of umbilical cord entanglement between the insertion sites whenever it is incidentally found. Based on the pathological description and the neonatal outcome reported for each entity, we conclude our descriptive review by establishing a new, clinically relevant classification of these umbilical cord anomalies.
Highlights
During embryogenesis, the four folds that emerge on the surface of the embryonic disc in the fourth embryonic week converge centrally in the umbilical area
The evaluation of the free cord loops that could reveal true knots, position, structure and helical pattern anomalies, is not stipulated in any guide. Both normal anatomy and malformations can be depicted by conventional 2D imaging, but color Doppler should be routinely used for umbilical cord assessment, especially in Diagnostics 2022, 12, 236 the second half of pregnancy; the benefit of 3D imaging techniques in the diagnosis of umbilical cord knot is indisputable, and enhanced by the HD-flow mode; the key to diagnosis is searching for the anomaly [17]
The velamentous cord insertion can be diagnosed by ultrasound, with a sensitivity of 69% to 100% and a specificity of 95% to 100%, in the second trimester [24]. This condition is reflected through variable decelerations and abnormal fetal heart rate variability in a non-stress test; this is frequently associated with vasa praevia, the most reliable method of diagnosis for which is the real-time color Doppler transvaginal ultrasound examination, which can depict the umbilical vessel pathway, which crosses the internal os or passes at less than 2 cm from it; this is used to study the enddiastolic velocity of the umbilical artery
Summary
The four folds that emerge on the surface of the embryonic disc in the fourth embryonic week converge centrally in the umbilical area. Imaging the umbilical cord during second trimester prenatal ultrasound examination is optional and limited to determining the number of vessels in the cord and assessment of the fetal insertion site; the study of placental insertion is proposed only for multiple gestations, even if the association of this pathology with pregnancy complications is recognized [6]. The evaluation of the free cord loops that could reveal true knots, position, structure and helical pattern anomalies, is not stipulated in any guide Both normal anatomy and malformations can be depicted by conventional 2D imaging, but color Doppler should be routinely used for umbilical cord assessment, especially in Diagnostics 2022, 12, 236 the second half of pregnancy; the benefit of 3D imaging techniques in the diagnosis of umbilical cord knot is indisputable, and enhanced by the HD-flow mode; the key to diagnosis is searching for the anomaly [17]. Extended analysis of the umbilical cord insertions and tract might offer the advantage of identifying and preventing adverse perinatal outcomes associated with certain umbilical cord abnormalities
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