Matias Alexandra, Ramalho Carla, Montenegro Nuno
Department of Obstetrics and Gynecology, Faculty of Medicine, Porto, Hospital of S. João, Porto, Portugal.
J Matern Fetal Neonatal Med. 2005 Aug;18(2):79-86. doi: 10.1080/14767050500232565.
Twin-twin transfusion syndrome is a devastating complication of monochorionic twin pregnancies. The presence of increased nuchal translucency thickness (NT) in one of the monochorionic twins has been associated with an increased risk of developing this syndrome. One of the most plausible mechanisms for increased nuchal translucency is heart failure, indirectly manifested by abnormal blood flow in the ductus venosus. We aimed to clarify the pathophysiology of increased NT found more frequently in monochorionic twins prone to develop twin-twin transfusion syndrome.
We present 50 cases of monochorionic twin pregnancies in which nuchal translucency thickness was measured and ductus venosus blood flow evaluation was performed at 11-14 weeks of gestation.
Whenever the fetuses of a twin pregnancy were found to have discrepant nuchal translucency thickness measurements and abnormal flow in the ductus venosus was found in the fetus with increased nuchal translucency thickness, twin-twin transfusion syndrome eventually developed. Progression to twin-to-twin transfusion syndrome was not observed in the twins displaying no intertwin difference in nuchal translucency thickness measurements and it was not observed in those with discrepant nuchal translucency thickness but normal flow in the ductus venosus of both fetuses. In the two cases which developed twin-to-twin transfusion syndrome, fetoscopic laser coagulation of the vascular anastomoses was successfully carried out at 18 weeks and normalization of the venous return was recorded.
Both increased nuchal translucency and abnormal flow in the ductus venosus in monochorionic twins may be early manifestations of haemodynamic imbalance between donor and recipient. The combined evaluation of both parameters in monochorionic twin pregnancies may constitute an effective method for identifying those at risk of developing twin-to-twin transfusion syndrome.
双胎输血综合征是单绒毛膜双胎妊娠的一种严重并发症。单绒毛膜双胎之一的颈项透明层厚度（NT）增加与发生该综合征的风险增加有关。颈项透明层增厚最合理的机制之一是心力衰竭，这通过静脉导管内异常血流间接表现出来。我们旨在阐明在易发生双胎输血综合征的单绒毛膜双胎中更频繁出现的NT增加的病理生理学机制。
我们报告了50例单绒毛膜双胎妊娠病例，在妊娠11 - 14周时测量了颈项透明层厚度并进行了静脉导管血流评估。
每当双胎妊娠的胎儿颈项透明层厚度测量值存在差异，且在颈项透明层增厚的胎儿中发现静脉导管血流异常时，最终都会发展为双胎输血综合征。在颈项透明层厚度测量值无双胎间差异的双胎中未观察到进展为双胎输血综合征的情况，在颈项透明层厚度有差异但两个胎儿静脉导管血流均正常的双胎中也未观察到。在发生双胎输血综合征的两例病例中，于18周成功进行了胎儿镜下血管吻合激光凝固术，并记录到静脉回流恢复正常。
单绒毛膜双胎中颈项透明层增加和静脉导管血流异常可能是供血儿与受血儿之间血流动力学失衡的早期表现。对单绒毛膜双胎妊娠的这两个参数进行联合评估可能构成一种识别有发生双胎输血综合征风险者的有效方法。
