分析超声对脐带打结的产前诊断价值及脐带打结与围产期结局的关系。

回顾性分析2015年1月至2019年12月间在安徽医科大学第一附属医院妊娠晚期出生或引产胎儿的产前超声及相关临床资料。总结分析脐带打结发生率及其与围产期结局的关系、产前二维超声和三维超声对脐带打结的诊断价值并归纳其声像图特征；并以产后诊断有脐带打结的病例为脐带打结组，其他正常胎儿中随机选择200例为非脐带打结组，采用独立样本t检验（正态分布）或秩和检验（偏态分布）对比分析2组大脑中动脉和脐动脉血流超声参数的差异。

5年间妊娠晚期娩出胎儿共40 346例，其中209例死亡（23例死于脐带并发症）。99例（0.25%，99/40 346）产后确诊为脐带打结，其中3例（3.03%，3/99）死于脐带打结，在晚孕期死亡胎儿中占比1.44%（3/209），在脐带并发症致死病因中占比13.04%（3/23）。产前二维超声提示可疑脐带打结15例，其中9例经三维超声诊断并最终经产后确诊。脐带打结二维超声特征性图像显示困难，可呈现为不同程度过度扭曲、堆积或“三叶草”状，而三维超声能够明确鉴别真假脐带打结，并可分为脐带松结、脐带紧结、脐带螺旋堆积和脐带扭曲堆积。脐带打结组胎儿大脑中动脉的血流阻力指数（0.75±0.07）低于非脐带打结组（0.76±0.06），差异具有统计学意义（t=1.988，P=0.048）。

二维超声发现可疑脐带打结，可联合三维超声提高脐带打结诊断的准确性；产前检出脐带打结利于产科医师进行管理并选择合适的分娩时机与适当的方式终止妊娠，避免胎儿围产期不良结局。胎儿大脑中动脉和脐动脉的超声血流参数正常时，不能排除脐带打结的存在。

To analyze the prenatal diagnostic value of ultrasound for umbilical cord knot (UCK) and the relationship between umbilical cord knot and perinatal outcome.

A retrospective analysis was conducted on the prenatal ultrasound and clinical data of newborns or induced fetuses in late pregnancy at the First Affiliated Hospital of Anhui Medical University from January 2015 to December 2019. The incidence of umbilical cord knot, its relationship with fetal perinatal outcome, and the diagnostic value of prenatal two-dimensional and three-dimensional ultrasound in umbilical cord knot and its image features were summarized and analyzed. The fetuses who were diagnosed as having umbilical cord knot after delivery were included as an umbilical cord knot group, and 200 normal fetuses were randomly selected as a non-umbilical cord knot group. The differences of ultrasonic parameters of the middle cerebral artery and the umbilical artery were compared between the two groups by independent sample t-test (normal distribution) or rank sum test (skewed distribution).

During 5 years, there were 40 346 fetuses born at our hospital in the third trimester, including 209 cases of stillbirths (23 died of umbilical cord complications). Ninety-nine (0.25%, 99/40 346) fetuses were confirmed with umbilical cord knot after delivery, of whom three (3.03%, 3/99) died of umbilical cord knot, accounting for 1.44% (3/209) of fetal deaths during late pregnancy and 13.04% (3/23) of umbilical cord complications. Prenatal 2D ultrasound showed 15 cases of suspicious umbilical cord knot, of which 9 were diagnosed by 3D ultrasound and were confirmed after delivery. It was difficult to display the characteristic images of umbilical cord knot by 2D ultrasound. 2D images can be classified as excessively distorted, stacked, or cloverleaf. 3D ultrasound can clearly identify the true and false umbilical cord knot, which can be divided into loose umbilical cord knot, tight umbilical cord knot, spiraling umbilical cord, and twisted and stacked umbilical cord. The resistance index of the middle cerebral artery in the umbilical cord knot group (0.75±0.07) was significantly lower than that in the no-umbilical cord knot group (0.76±0.06; t=1.988, P=0.048).

2D ultrasound combined with 3D ultrasound can improve the prenatal diagnostic accuracy for umbilical cord knot. The prenatal diagnosis of umbilical cord knot is beneficial for obstetricians to choose the proper time and way of delivery to terminate pregnancy to avoid perinatal adverse outcomes. The presence of umbilical cord knot cannot be ruled out when the ultrasonographic blood flow parameters of the middle cerebral artery and umbilical artery are normal.