早孕期超声指标对复杂性单绒毛膜双胎的预测价值

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

目的探讨早孕期超声指标对复杂性单绒毛膜双羊膜囊(monochorionic diamniotic, MCDA)双胎的临床预测价值。方法本研究为回顾性研究。研究对象为2013年1月至2018年1月在中山大学附属第一医院经超声诊断为MCDA双胎的孕妇。根据是否发生复杂性MCDA(包括TTTS、sIUGR、TAPS等),将其分为正常MCDA双胎组、双胎输血综合征(twin-twin transfusion syndrome, TTTS)组、选择性宫内生长受限(selective intrauterine growth restriction, sIUGR)组和双胎贫血-红细胞增多序列(twin anemia-polycythemia sequence, TAPS)组。分别记录各组孕11~14周超声的双胎颈项透明层(nuchal translucency, NT)厚度、头臀长、脐带插入位置、静脉导管频谱等资料。采用t检验、χ2检验(或Fisher精确概率法)、多因素logistic回归分析,并绘制受试者工作特性(receiver operating characteristic, ROC)曲线进行分析。结果(1)纳入本研究的MCDA双胎共430例,包括TTTS组152例,sIUGR组142例,TAPS组7例,正常MCDA双胎组129例。TAPS组病例数较少,未行进一步分析。(2)TTTS组双胎NT差异大于正常MCDA双胎组[(21.5±16.0)%与(14.6±13.5)%,t=-3.533,P<0.001]。双胎NT差异预测TTTS的ROC曲线下面积(area under the curve, AUC)为0.649。分层分析显示,MCDA双胎NT差异20%是最佳预测界值,其预测TTTS的敏感度为57.9%,特异度为70.6%。(3)sIUGR组双胎NT和头臀长差异大于正常MCDA双胎组[NT:(27.8±21.3)%与(14.6±13.5)%,t=-5.556,P<0.001;头臀长:(8.6±6.9)%与(5.4±4.4)%,t=-3.144,P=0.002],脐带插入差异发生率高于正常MCDA双胎组[47.9%(68/142)与13.9%(18/129),χ2=35.929,P<0.001]。双胎NT和头臀长差异预测sIUGR的ROC曲线下面积分别为0.675和0.649。对MCDA双胎NT和头臀长差异进行分层分析发现,双胎NT差异预测sIUGR的界值为20%,敏感度为53.1%,特异度为72.1%;双胎头臀长差异预测sIUGR最佳界值为10%,敏感度为34.7%,特异度为83.8%。以双胎NT、头臀长和脐带插入差异为指标进行多因素logistic回归分析发现,双胎脐带插入差异是sIUGR的危险因素(OR=7.165,95%CI:2.637~19.472)。结论早孕期MCDA双胎NT差异>20%时,发生TTTS的风险增加。双胎头臀长差异>10%,或NT差异>20%,亦或脐带插入异常,是发生sIUGR的危险因素。

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.