MRI changes of pelvic floor and pubic bone observed in primiparous women after childbirth by normal vaginal delivery

OBJECTIVE: To identify and characterize changes in the pelvic floor and pubic bone, using magnetic resonance imaging, in primiparous women with normal vaginal delivery, in comparison with nulliparous women. METHODS: Pelvic MR images from ten primiparous women, 6–7 weeks after normal vaginal delivery, and ten nulliparous women were obtained from January to April 2014. The selected women were scanned using a multiplanar T2FRFSE sequence and T2fsFRFSE sequence. Changes in the pelvic floor and pubic bone in primiparous women, including tears of the levator ani fibers, pubic bone edema, and fractures, were assessed on the MR images in comparison with images from normal nulliparous women. Injury to the levator ani was evaluated and scored. The incidence, location and the extent of injury to the levator ani and pubic bone were characterized further. RESULTS: Eight out of ten primiparous women had imaging abnormalities after normal vaginal delivery. Three women had unilateral tears of the pubococcygeus, in which the defect in the muscle was located at or near its origin at the pubic bone, and one had a pubococcygeus tear accompanied by bilateral spilling of the vagina. Four women had partial tears of the iliococcygeus: one was a bilateral tear, and three were unilateral. None had a tear of the coccygeus. Eight women had pubic bone marrow edema; one was accompanied by a pubic bone fracture line. None of the nulliparous women had any abnormality of the pelvic floor and pubic bone. CONCLUSION: Abnormalities of the pelvic floor and pubic bone were observed in primiparous women but not in nulliparous women. In primiparous women, most levator ani muscle tears are at or near the point of origin, and pubococcygeus injuries are usually accompanied by pubic bone marrow edema.