Placenta accreta spectrum (PAS) is associated with significant maternal morbidity mainly related to blood loss. Pre-operative planning is aided by antenatal ultrasound and magnetic resonance imaging. We wanted to find out whether three-dimensional (3D) models from MRI scans were accurate when compared with surgical and pathological findings.
MR images with varying severity of PAS (n = 4) were modeled using 3D Slicer. Placenta, bladder, and myometrial defects were modeled. Myometrial defects at three different uterine locations were included—anterior, lateral and inferior. 3D models were used to identify the relationship between the myometrial defect and the internal cervical os. Findings were validated in a larger series of PAS cases (n = 14) where patterns of invasion were compared with estimated blood loss and distance from defect to the inner part of the cervix.
The defect illustrated in the four 3D models correlates to both surgical and pathological findings in terms of depth and pattern of invasion, location of defect, bladder involvement. Blood loss and topography of the defect from 3D modeling were examined in 14 further cases. Inferior defects were associated with increased blood loss compared with anterior defects. Increased distance from cervix was associated with reduced blood loss and this was statistically significant (R2 = 0.352, P = 0.01).
Three-dimensional models of PAS provide an accurate preoperative description of placental invasion and should be investigated as a tool for selecting patients for uterine-conserving surgery.
written by Karen Mulligan.
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