Placenta accreta spectrum: the pattern and character of intraplacental blood flow by color and spectral Doppler.

ABSTRACT

PURPOSE: To characterize intraplacental blood flow patterns in placenta accreta spectrum (PAS) with color and spectral Doppler imaging. METHODS: Thirty-two patients at risk for PAS underwent ultrasound imaging with both color and spectral Doppler. The placenta was inspected for areas of vascularity by color Doppler, particularly within the lower uterine segment. Spectral Doppler waveforms were obtained from these vessels and categorized as either intraplacental or subplacental (myometrial), venous or arterial, fetal or maternal (based on heart rate). Arterial waveforms were measured for heart rate, peak systolic velocity, end diastolic velocity, and resistive index. Statistical comparisons were made between cases with and without PAS using Fisher exact tests (categorical variables) and Mann-Whitney U tests (numerical indices). Interobserver agreement was characterized with kappa coefficients. RESULTS: At delivery, there were 19 cases with PAS and 13 without PAS. On ultrasound studies, clustered intraplacental vascularity was found in the lower uterine segment in 66% of cases (95% of PAS cases and 23% cases without PAS; p < 0.0001). Maternal arterial waveforms were found within the vascular cluster in 84% of PAS cases and 15% of cases without PAS (p < 0.0001). A traversing fetal artery was found within the vascular cluster in 56% of cases (84% PAS cases and 15% cases without PAS; p = 0.001). Venous waveforms were found in 84% of PAS cases and 15% of cases without PAS. Interobserver agreement was good to excellent. CONCLUSION: Intraplacental blood flow pattern in PAS is characterized by an intraplacental vascular cluster containing low-resistance maternal arterial flow and transplacental fetal arteries.