Background  The adverse outcome of hypertensive disorder complicating pregnancy seriously endangers the health of mother and child, and the ability of early prediction of clinical indicators is limited at present. Superb micro-vascular imaging (SMI) provides quantitative indicators of placental perfusion, which may provide early prediction of adverse outcomes.

  Objective  To explore the value of quantitative evaluation of SMI in placental vascular perfusion of hypertensive disorder complicating pregnancy.

  Methods  From October 2019 to October 2021, pregnant women in the third trimester (28 w - 32 w) with placenta perfusion evaluated by routine ultrasound examination and SMI in our center were included in this study. The blood flow perfusion of placenta in each group was observed by SMI, and the quantitative indexes of vascularization index (VI), the ratio of the peak systolic blood flow velocity of umbilical artery to the end diastolic blood flow velocity (S/D) and the blood pressure of pregnant women were recorded, and the pregnancy outcomes were followed up until one month after delivery. Low birth weight, fetal distress, neonatal asphyxia and perinatal death were the adverse pregnancy outcomes. The sensitivity and specificity of the above indicators were analyzed, ROC curve was drawn, and the area under the curve (AUC) and each cut-off values were calculated.

  Results  There were 90 cases in the normal control group, and 52 cases in the hypertensive disorder of pregnancy (HDP) group, including 35 cases with gestational hypertension (GHT), 12 cases with preeclampsia (PE) and 5 cases with eclampsia. In the HDP group, there were 7 cases of low birth weight, 10 cases of fetal distress and 6 cases of neonatal asphyxia, and the incidences were higher than those in normal group(3cases, 4cases, 1case, respectively) (all P < 0.05). The SMI placental perfusion map of pregnant women in the HDP group showed that the diameter of villous blood vessels in placenta was uneven and irregular, showing only the primary and secondary villous blood vessels near the surface, without the uterine spiral artery and its branches. Compared with the normal group(VI, 16.2), the placental median VI values of the GHT group, the PE group and the eclampsia group were 10.2, 7.0 and 4.1, respectively (P < 0.05). There was no significant difference in S/D ratio between the normal group and the GHT group, the PE group and the eclampsia group (P > 0.05). ROC analysis shows that SBP, DBP, S/D, VI and their combined application could predict the adverse pregnancy outcome, with ROC-AUC (95% CI) of 0.740 (0.569-0.911), 0.719 (0.452-0.972), 0.698 (0.434-0.959), 0.769 (0.545-0.969), 0.863(0.782-0.951). Among them, the diagnostic efficiency of combined application was higher.

  Conclusion  SMI technology can be used in late pregnancy to assess the severity of hypertensive disorder complicating pregnancy early and quantitatively, and VI has a high clinical value in predicting adverse pregnancy outcomes.