Static Anatomical Measurements and Dynamic Endometrial Peristalsis in Young Women During Different Menstrual Cycle Phases: A Study with 3 T MRI.

RATIONALE AND OBJECTIVES: To investigate cyclic variations in static uterine anatomy and dynamic endometrial peristalsis across menstrual phases using 3T MRI. METHODS AND MATERIALS: Forty-two healthy nulliparous women prospectively underwent 3T MRI at three standardized phases: menstrual (MP), ovulatory (OP), and luteal (LP). Static uterine dimensions and layered wall thickness were measured on T2-weighted imaging. Dynamic endometrial peristalsis was assessed using HASTE cine sequences, quantifying frequency, direction, and amplitude separately in anterior and posterior uterine walls. RESULTS: Significant phase-specific differences were observed in uterine corpus parameters and peristaltic metrics, whereas cervical parameters remained stable. Uterine volume correlated most strongly with uterine height, while cervical volume correlated with length (OP, LP) and width (MP). Endometrial peristalsis showed distinct directional patterns: cervico-fundal waves predominated in OP, fundo-cervical waves in MP. Anterior wall peristalsis frequency accurately predicted the ovulatory phase. Notably, peristaltic amplitude differed significantly between anterior and posterior uterine walls exclusively during OP. CONCLUSION: Static uterine morphology and dynamic endometrial peristalsis undergo predictable, hormone-driven cyclic remodeling in young women. The novel observation of anteroposterior amplitude asymmetry during the ovulatory window highlights localized functional specialization. These findings provide a normative MRI reference for uterine physiology and a basis for investigating uterine dysmotility in reproductive disorders.