Department of Obstetrics and Gynecology, Neue Frauenklinik Luzern, Luzern, Switzerland.
Ultrasound Obstet Gynecol. 2012 May;39(5):505-9. doi: 10.1002/uog.9085.
Our purpose was to evaluate the antenatal incidence of single umbilical artery (SUA) in twin pregnancies according to chorionicity and to assess its relationship with outcome.
Consecutive twin pregnancies undergoing ultrasound evaluation at our institutions were included. A targeted sonographic evaluation of the umbilical cord and vessels was performed in all cases. Chorionicity was determined according to standard ultrasound criteria.
A total of 174 twin pregnancies, 100 dichorionic (DC) and 74 monochorionic (MC), were included in the study. An SUA was identified in 17 (9.8%) pregnancies, and in 18 (5.2%) fetuses. No difference was found in the incidence of SUA in DC and MC twins. Among affected pregnancies, all but one DC twin pregnancy were discordant for SUA. Structural and/or chromosomal abnormalities were present in 27.8% of fetuses with SUA. The prevalence of small-for-gestational-age fetuses and of discordant birth weight (> 20% discordance) was higher in the SUA group than in the rest of the population, although these differences were not statistically significant. Twin pairs discordant for SUA had significantly higher weight discordance than those with normal umbilical cords. The sonographic cross-sectional area of the SUA did not appear to show the typical adaptive dilatation usually seen in singleton pregnancies with SUA.
The incidence of SUA in twins is higher than in singletons, with no difference between MC and DC twins. Intrapair discordance for SUA in identical twins provides evidence against an exclusively genetic origin of this anomaly. The apparent failure of compensatory dilatation of the umbilical artery in twins with SUA may explain in part the higher risk for fetal growth restriction in these cases.
本研究旨在评估根据绒毛膜性评估双胎妊娠中单脐动脉（SUA）的产前发生率，并评估其与结局的关系。
连续纳入在本机构行超声检查的双胎妊娠。所有病例均行脐带及血管的靶向超声检查。绒毛膜性根据标准超声标准确定。
本研究共纳入 174 例双胎妊娠，100 例双绒毛膜性（DC）和 74 例单绒毛膜性（MC）。发现 17 例（9.8%）妊娠和 18 例（5.2%）胎儿存在 SUA。DC 和 MC 双胎妊娠的 SUA 发生率无差异。在受影响的妊娠中，除 1 例 DC 双胎妊娠外，其余均为 SUA 不一致。SUA 胎儿中存在结构和/或染色体异常的比例为 27.8%。SUA 组胎儿小于胎龄儿和双胎体重差异（>20%差异）的发生率高于其余人群，但差异无统计学意义。SUA 不一致的双胎对体重差异明显大于脐带正常的双胎。SUA 的超声横截面积似乎没有表现出通常在 SUA 单胎妊娠中见到的典型适应性扩张。
双胎妊娠 SUA 的发生率高于单胎妊娠，MC 和 DC 双胎妊娠之间无差异。同卵双胞胎之间的 SUA 不一致为该异常的遗传起源提供了证据。SUA 双胞胎中脐动脉代偿性扩张的明显失败可能部分解释了这些情况下胎儿生长受限的风险增加。
