Acharya G, Wilsgaard T, Rosvold Berntsen G K, Maltau J M, Kiserud T
Department of Obstetrics and Gynecology, University Hospital of Northern Norway, N-9038 Tromsø, Norway.
Ultrasound Obstet Gynecol. 2006 Aug;28(2):150-5. doi: 10.1002/uog.2711.
It has been suggested that constriction of the umbilical vein (UV) at the umbilical ring has hemodynamic effects. We aimed to determine the occurrence and extent of such constriction in serial observations.
This was a prospective longitudinal study of UV velocities at the umbilicus measured at approximately 4-week intervals between 19 and 42 weeks' gestation in 129 low-risk singleton pregnancies. Each participant was examined three to five times. Multilevel modeling was used to construct the reference ranges and to test associations between variables.
Gestational age-specific reference percentiles of UV velocities at the umbilicus were established based on 469 observations. Fetuses were able to alter the UV velocities considerably during the second half of pregnancy, signifying a varying degree of UV constriction. Of a total of 129 fetuses, 56 (43.4%) never had high UV blood velocity (i.e. > 46 cm/s, the highest quartile), 42 (32.6%) fetuses had high UV blood velocity on one occasion and 31 (24.0%) fetuses on two or more occasions. In 36 (27.9%) fetuses the UV velocity at the umbilical ring was > 300% of the mean gestational age-specific reference value at the intra-abdominal section on at least one occasion. Constriction of the UV at the umbilical ring did not affect the pulsatility of the umbilical artery, and was not associated with adverse perinatal outcome in this study.
Low-risk fetuses may well constrict the UV at the abdominal wall with velocities extending over wide ranges on one or more occasions during the second half of pregnancy. Rather than being a risk for complications, the constriction seems to be part of physiological development and possibly a regulatory mechanism.
有人提出，在脐环处压迫脐静脉（UV）具有血流动力学效应。我们旨在通过系列观察确定这种压迫的发生率和程度。
这是一项前瞻性纵向研究，对129例低风险单胎妊娠在妊娠19至42周期间每隔约4周测量一次脐部UV流速。每位参与者接受检查三至五次。采用多水平模型构建参考范围并检验变量之间的关联。
基于469次观察建立了脐部UV流速的孕周特异性参考百分位数。胎儿在妊娠后半期能够显著改变UV流速，这表明UV存在不同程度的压迫。在总共129例胎儿中，56例（43.4%）从未有过高的UV血流速度（即>46 cm/s，最高四分位数），42例（32.6%）胎儿有过一次UV血流速度高的情况，31例（24.0%）胎儿有过两次或更多次。在36例（27.9%）胎儿中，脐环处的UV流速至少有一次超过腹腔内段孕周特异性平均参考值的300%。本研究中，脐环处UV的压迫不影响脐动脉的搏动性，且与不良围产期结局无关。
低风险胎儿在妊娠后半期可能会在腹壁处压迫UV，其流速在一个或多个时段内会有很大范围的变化。这种压迫似乎不是并发症的风险因素，而是生理发育的一部分，可能还是一种调节机制。
