To perform placental microflow perfusion imaging (MV-Flow) in early low-risk and high-risk pregnancies, and explore the characteristics of placental microvascular index (MVI) in low-risk and high-risk pregnancies and its predictive value for adverse pregnancy outcome.

Pregnant women with singleton pregnancies at 11 to 13⁺⁶ weeks of gestation who underwent regular prenatal check-ups at Sichuan Maternal and Child Health Hospital from January to December 2022 were selected. A high-risk pregnancy was defined as the presence of one high-risk factor or two moderate-risk factors, and a low-risk pregnancy was defined as a singleton pregnancy in a mother with no comorbidities. Placental MV-FIow was performed in early pregnancy on 95 cases of low-risk pregnancies and 44 cases of high-risk pregnancies. Placental MVI, vascularization index, flow index, vascularization-flow, placental volume, and uterine artery pulse index of the two groups of pregnant women in early pregnancy were measured, and the basic clinical data of the pregnant women, newborn birth weight and gestational age, and adverse pregnancy were collected. The χ² test/Fisher's exact test and Wilcoxon rank sum test were used to compare the differences in the above variables between the high-risk group and low-risk group. The intraclass correlation coefficient test was used to analyze the consistency of MVI measurements. Multiple linear regression was used to analyze the correlation between the basic parameters of pregnant women and MVI values in the low-risk group, and logistic regression was used to evaluate the effectiveness of each parameter in predicting adverse pregnancy outcome.

The MVI reference value of the low-risk pregnancy group was 57.30 (46.10-67.47), and the corresponding value of the high-risk pregnancy group was 48.09 (37.52-58.63). The placental MVI of the high-risk group was significantly lower than that of the low-risk group (Z=-3.446, P<0.001). There were statistically significant differences in adverse pregnancy outcomes (11 vs 9), maternal age [30 (28, 35) years vs 29 (27, 31) years], and aspirin was used (13 vs 6) between the high-risk group and the low-risk group (χ²=5.885, P=0.015; Z=2.385, P=0.017; χ²=13.751, P<0.001). In the low-risk group, there was a weak linear correlation between gestational age and MVI (r²=0.081, P<0.05), and the MVI value increased with increasing gestational age. Gravidity had a certain impact on early placental MVI value (B=4.022, t=3.190, P<0.05). There was no significant difference in the prediction of adverse pregnancy outcomes by early placental MVI in the two groups of pregnant women (P>0.05 for both). One case in the low-risk group had an early miscarriage with a low MVI value (24.6).

MV-Flow technology can quantitatively display placental microperfusion in early low-risk and high-risk pregnancies. There is a certain correlation between gestational age and gravidity and placental microblood perfusion in early pregnancy. Placental MVI in early high-risk pregnancies is significantly lower than that in low-risk pregnancies. However, it has not been found that abnormal placental MVI in early pregnancy will lead to adverse pregnancy.