The Value Of Prenatal Ultrasound In Diagnosing Umbilical Cord Abnormalities And The Effect Of Umbilical Cord Knot On Fetal Perinatal Outcome

Objective: To analyze the prenatal diagnostic value of ultrasound for umbilical cord abnormalities(UCA)and the relationship between umbilical cord knot(UCK)and fetal perinatal outcome.Methods: Retrospective analysis was conducted on the prenatal ultrasound and clinical data of newborns or induced fetuses in the third trimester in our hospital from January2015 to December 2019.The inclusion criteria included fetuses which delivered normally and stillbirth at 28 weeks or more.And ultrasound examination and clinical data were complete.The exclusion criteria included incomplete prenatal ultrasound examination,clinical data and artificial termination of pregnancy at late pregnancy.Diagnostic criteria of prenatal ultrasound for UCK: the accumulation of umbilical cord showed“clover or noose sign”by two-dimensional ultrasound;The three-dimensional structure of umbilical cord true knot was presented by three-dimensional ultrasound.The gold standard for diagnosis of UCK: the clinician confirmed that there was UCK on the umbilical cord postpartum or post-induction.The incidence,mortality and the prenatal ultrasound diagnostic value of umbilical cord abnormalities and the relationship between UCK and fetal perinatal outcome were summarized and analyzed.The fetuses who were diagnosed as UCK after delivery were the UCK group,and the control group was 200 cases randomly selected from other normal fetuses.The differences of ultrasonic parameters and related clinical parameters were compared between the two groups by independent sample T-test(normal distribution)or rank sum test(skewed distribution).Results: During 5 years,there were 40346 fetuses were born in our hospital,including8239 cases were diagnosed with umbilical cord abnormalities after delivery,209 cases stillbirths and 23 cases died from umbilical cord abnormalities in the third trimester.The diagnostic rates of cord placental insertion site abnormalities,umbilical cord prolapse,nuchal cord,single umbilical artery,umbilical cord torsion,body cord and UCK were99.8%,99.3%,98.1%,93.2%,82.6%,70.1%,9.1%,respectively.The suggestion of excessive long umbilical cord,short umbilical cord,umbilical cord edema and thrombosis of the umbilical vessels was not found by prenatal two-dimensional ultrasound.Fetal death due to umbilical cord abnormalities accounted for 11% in the third trimester.The highest cause was umbilical cord torsion,accounting for 30.43%.99 fetuses were confirmed with UCK by postnatal diagnosis(including 3 stillbirths died of UCK,accounting for 3% of the diagnosis of UCK).It was difficult to display the characteristic images of UCK by two-dimensional ultrasound.Two-dimensional images can be classified as excessively distorted,stacked or cloverleaf.The three-dimensional ultrasound can clearly identify the true and false UCK,which can be divided into loose UCK,tight UCK,spiraling umbilical cord and twisted and stacked umbilical cord.Prenatal two-dimensional ultrasound showed 15 cases of suspicious UCK,of which 9cases were diagnosed by three-dimensional ultrasound and postnatal confirmed.The resistance index of middle cerebral artery in the UCK group was lower than that in the normal control group(P<0.05).There were statistically significant differences in the maternal age,multiparty,gestational weeks,gestational diabetes mellitus,amniotic fluid volume and length of umbilical cord between the two groups(P<0.05).Conclusions: The detection rate of cord placental insertion site abnormalities,umbilical cord prolapse,nuchal cord,single umbilical artery,umbilical cord torsion and body cord are all very high by two-dimensional ultrasound except UCK,excessive long umbilical cord and short umbilical cord,umbilical cord edema and thrombosis of the umbilical vessels.Umbilical cord abnormalities accounted for 11% of all fetal death causes in the third trimester.Prenatal ultrasound diagnosis of umbilical cord abnormalities may provide a basis for clinical interventions to reduce fetal mortality.The incidence of UCK is only 0.25%,but mortality accounts for 1.4% of the fetal death and accounts for3% in fetuses with UCK in the third trimester.With the maternal age,parity,amniotic fluid volume and cord length increased,the risk of UCK is increased.Two-dimensional ultrasound is combined with three-dimensional ultrasound can improve the prenatal diagnostic accuracy of UCK.The presence of UCK could not be ruled out when ultrasound show normal flow parameters of middle cerebral artery and umbilical artery in the fetus.