Anatomic changes in the pelvis after uncomplicated vaginal delivery: evaluation with serial MR imaging.

Abstract

To demonstrate the normal involution process of the post-partum pelvis with serial magnetic resonance (MR) imaging. MR imaging was performed in 14 women after uncomplicated vaginal 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; eight women were examined only within 30 hours of delivery. The dimensions and signal intensity of the uterus and cervix and the appearance of other pelvic structures were evaluated. 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 visible before 2 weeks; however, it was visible in all cases at 6 months. The outer cervical stroma had high signal intensity less than 30 hours after delivery and intermediate signal intensity thereafter. The inner cervical stroma was visible as a low-signal-intensity stripe on all images. Knowledge of the normal MR appearance of the involuting postpartum pelvis provides a baseline for interpretation of MR images obtained during this period.