Study On Predictive Indexs Of Twin-to-twin Transfusion Syndrome

Objective:To explore the value of nuchal translucency (NT), blood flow in ductus venosus (DV) and the way of umbilical cord insertion in predicting twin-twin transfusion syndrome (TTTS).Methods:A retrospective study of 134 monochorionic diamniotic (MCDA) patients whose prenatal examination and delivery were taken in the First Affiliateted Hospital of Kunming Medical University from January 2010 to November 2015 was enrolled. The patients were divided into two groups:TTTS group (n=17) and non-TTTS group (n=117). In TTTS group, there were 12 cases with NT values,11 cases with blood flow in DV,15 cases with umbilical cord attached type data, and 9 cases with all of above, and in non-TTTS group, the cases was 64,58,115 and 50 respectively. The sensitivity, specificity, positive predictive value and negative predictive value of each index was calculated.Results:The incidence of TTTS in MCDA twins was 12,7%(17/134).① The incidence of two fetal NT difference of 20% or more in TTTS group (66.6%,8/12) was significantly higher than that in the non-TTTS group (31.2,20/64), (P<0.05). The sensitivity, specificity, positive predictive value and negative predictive value of two fetal NT difference of 20% or more in predicting TTTS were 66.7%,68.8%,28.6% and 91.7% respectively.②The incidence of abnormal fetal DV blood flow (absent or reversed a-wave) in at least one of the fetuses in TTTS group (62.5%,5/8) was significantly higher than that in the non-TTTS group (9.8%,6/61),(P< 0.05). The sensitivity, specificity, positive predictive value and negative predictive value of abnormal fetal DV blood flow in predicting TTTS were 62.5%,90.2%,45.5% and 94.8% respectively.③The incidence of velamentous or marginal cord insertion in TTTS group (53.3%,8/15) was significantly higher than that in the non-TTTS group (12.2,14/115), (P<0.05). The sensitivity, specificity, positive predictive value and negative predictive value of velamentous or marginal cord insertion in predicting TTTS were 53.3%,87.8%,36.4% and 93.5% respectively.④The best predictor of TTTS was NT difference of 20% or more between twins [area under the curve (AUC)=0.773, P<0.05,95% CI,0.582-0.965]. The second predictor of TTTS was abnormal DV blood flow (absent or reversed a-wave) in at least one of the fetuses (AUC=0.748, P<0.05,95% CI,0.540～0.956). The third predictor was velamentous or marginal cord insertion (AUC=0.718, P<0.05,95% CI,0.511-0.925).Conclusions:①NT differential value of 20% or more,abnormal DV blood flow, velamentous or marginal cord insertion may have certain predictive value for TTTS. ④The best predictor of TTTS was NT differential value of 20% or more between twins.