Fig. 6

Maternal–fetal metabolites in the evaluation of fetal brain injury in MCDA twins. A Pie plot showing the proportion of abnormal signal in the brain structure, white matter, and choroid plexus, detected by cerebral ultrasound, in either the sFGR (n = 68) or MCDA (n = 88) group. B ROC curves of models constructed based on each significantly differential maternal metabolites for the prediction of fetal brain injury. C ROC curve of models constructed based on the combination of significantly differential maternal metabolites for the prediction of fetal brain injury. The five-AUC presents the predictive effectiveness of the combination of five metabolites, including l-serine, l-histidine, and l-arginine in the first trimester, creatinine in the second trimester, and l-glutamic acid in the third trimester. The four-AUC presents the predictive effectiveness of the optimized combination of four metabolites, including l-serine, l-histidine, and l-arginine in the first trimester, creatinine in the second trimester. D ROC curves of models constructed based on each significantly differential cord plasma metabolite for the prediction of fetal brain injury. E ROC curve of models constructed based on the combination of significantly differential cord plasma metabolite for the prediction of fetal brain injury. The two-AUC presents the predictive effectiveness of the combination of two metabolites, including l-arginine and creatinine in cord plasma. The dots on the broken lines in C and E represent the best cut-off value, and the values in the figure represent the best cut-off value (sensitivity, specificity). The shadow around the linear regression trendline shows the 95% confidence interval (CI). The P value in C and E were shown as the significant difference between model A and model B; sFGR, selective fetal growth restriction; MCDA, normal monochorionic diamniotic twins; FT, first trimester, ST, second trimester, TT, third trimester; ROC, receiver operating characteristic; AUC, area under curve; CP, cord plasma; MP, maternal plasma; P < 0.05 was considered statistically significant