Predictive value of first-trimester ultrasound markers for complicated monochorionic diamniotic twins

Abstract

Objective To investigate the value of first-trimester ultrasound parameters in predicting complicated monochorionic diamniotic (MCDA) twins. Methods In this retrospective study, pregnant women diagnosed as MCDA twins by ultrasound in the First Affiliated Hospital of Sun Yat-sen University from January 2013 to January 2018 were recruited and divided into the following four groups: non-complicated MCDA twins group, twin-twin transfusion syndrome (TTTS) group, selective intrauterine growth restriction (sIUGR) group and twin anemia-polycythemia sequence (TAPS) group. Thickness of nuchal translucency (NT), crown-rump length (CRL), umbilical cord insertion (UCI) and ductus venosus (DV) flow at 11-14 weeks of gestation were recorded. The predictive value for complicated MCDA twins was analyzed using t-test, Chi-square (or Fisher's exact) test, multivariate logistic regression analysis and receiver operating characteristic (ROC) curve. Results (1) A total of 430 MCDA twin pregnancies were included in this study with 152 in the TTTS group, 142 in the sIUGR group, seven in the TAPS group and 129 in the normal MCDA twins group. No further analysis was performed on the TAPS group due to the small sample size. (2) NT discordance in twins of the TTTS group was significantly greater than that in the normal MCDA twins group[(21.5±16.0)% vs (14.6±13.5)%, t=-3.533, P<0.001]. The area under ROC curve (AUC) of TTTS predicted by NT discordance was 0.649. Stratified analysis showed that TTTS was best predicted when NT discordance was 20% with the sensitivity of 57.9% and specificity of 70.6%. (3) The sIUGR group had greater discordance in CRL and NT and higher UCI discordance than the normal MCDA twins group [NT: (27.8±21.3)% vs (14.6±13.5)%, t=-5.556, P<0.001; CRL: (8.6±6.9)% vs (5.4±4.4)%, t=-3.144, P=0.002; UCI: 47.9% (68/142) vs 13.9% (18/129), χ2=35.929, P<0.001]. The AUC of sIUGR was 0.675 predicted by NT discordance and 0.649 by CRL discordance. Stratified analysis showed that NT discordance of 20% and CRL discordance of 10% were the best prediction for sIUGR with the sensitivity of 53.1% and 34.7% and specificity of 72.1% and 83.8%, respectively. Multivariate logistic regression analysis suggested that UCI discordance was the risk factor for sIUGR (OR=7.165, 95%CI: 2.637-19.472). Conclusions MCDA twins with NT discordance greater than 20% during early pregnancy are at increased risk for TTTS. CRL discordance greater than 10%, NT discordance greater than 20% and abnormal UCI are risk factors for sIUGR. Key words: Twins, monozygotic; Pregnancy trimester, first; Ultrasonography, prenatal; Nuchal translucency measurement; Fetofetal transfusion; Fetal growth retardation; Forecasting