Exploration of normal placental blood flow characteristics in middle and late pregnancy based on microvascular flow...

To explore the micro blood flow characteristics of normal singleton pregnancy placenta in middle and late pregnancy based on microvascular flow (MV-Flow) imaging.

We conducted a retrospective cohort study. Clinical records and placental ultrasound images of 485 patients in mid to late pregnancy with normal fetal development who underwent MV-Flow microvascular imaging in The First Affiliated Hospital of Anhui Medical University from January 2023 to December 2023 were retrospectively analyzed. The gestational age of patients ranged from 22 to 38 weeks, and the biological measurements of the fetus during pregnancy were within the normal range. The patients were divided into six groups according to gestational age: 22-24W, 25-27W, 28-30W, 31-33W, 34-36W, and 37-39W.

During the middle and late stages of normal pregnancy, the placental microvasculature displayed grade three or higher blood flow branches. As the gestational age increased, the peak systolic velocity (PSV) of the fetal umbilical artery (UA) and middle cerebral artery (MCA) gradually increased. The UA pulsatility index (PI), MCA-PI, and ductus venosus (DV) - PI gradually decreased with the gestational age (all P<0.05). There were statistically significant differences in the PSV and PI of various branches of the chorionic vascular tree in different gestational age groups (all P<0.05). However, there was no statistically significant difference in vascular index from MV-Flow (VI^MV) (P>0.05), with no significant changes at different gestational weeks.

Placental microvascular imaging based on MV-Flow can demonstrate a gradual increase in the microvascular flow velocity inside the placenta and a gradual decrease in the blood flow resistance with gestational age.