ANATOMIC CHANGES IN THE PELVIS ALTER UNCOMPLICATED VAGINAL DELIVERY -EVALUATION WITH SERIAL MR-IMAGING

PURPOSE: To demonstrate the normal involution process of the postpartu m pelvis with serial magnetic resonance (MR) imaging. MATERIALS AND ME THODS: MR imaging was performed in 14 women after uncomplicated vagina l delivery. Six women underwent serial MR examinations at less than 30 hours and at 1 week, 2 weeks, 6 weeks, and 6 months after delivery; e ight women were examined only within 30 hours of delivery. The dimensi ons and signal intensity of the uterus and cervix and the appearance o f other pelvic structures were evaluated. RESULTS: The mean length of the uterine corpus was 13.8 cm within 30 hours of delivery and 5.0 cm at 6 months. The mean length of the cervix was 5.6 cm within 30 hours of delivery and 2.9 cm at 6 months. The junctional zone was not visibl e before 2 weeks; however, it was visible in all cases at 6 months. Th e outer cervical stroma had high signal intensity less than 30 hours a fter delivery and intermediate signal intensity thereafter. The inner cervical stroma was visible as a low-signal-intensity stripe on all im ages. CONCLUSION: Knowledge of the normal MR appearance of the involut ing postpartum pelvis provides a baseline for interpretation of MR ima ges obtained during this period.