Randomized trial of cesarean vs vaginal delivery for effects on the pelvic floor in squirrel monkeys

Abstract

Objectives Vaginal delivery is a risk factor in pelvic floor disorders. We previously described changes in the pelvic floor associated with pregnancy and parturition in the squirrel monkey, a species with a human-like pattern of spontaneous age and parity associated pelvic organ prolapse. The potential to prevent or diminish these changes with scheduled cesarean section has not been evaluated. In a randomized, controlled trial, we compare female squirrel monkeys undergoing spontaneous vaginal delivery with those undergoing scheduled primary cesarean section for pelvic floor muscle volumes, muscle contrast changes, and dynamic effects on bladder neck position. Study Design Levator ani, obturator internus, and coccygeus muscle volumes and contrast uptake were assessed by magnetic resonance imaging in 20 nulliparous females examined prior to pregnancy, a few days after delivery, and 3 months post-partum. The position of bladder neck relative to boney reference line also was assessed with abdominal pressure using dynamic magnetic resonance imaging. Results Baseline measurements of 10 females randomly assigned to scheduled primary cesarean sections were not different from those of 10 females assigned to spontaneous vaginal delivery. Levator ani and obturator internus muscle volumes did not differ between groups, while volumes were reduced (p < 0.05) in the observation immediately after pregnancy. The coccygeus muscles increased (p < 0.05) immediately after delivery for females in the spontaneous vaginal delivery group, but not for females in the scheduled cesarean section group. Position of the bladder neck descended (p < 0.05) by 3 months post-partum in both groups. Conclusions Scheduled cesarean delivery diminishes changes in coccygeus muscle volume and contrast reported to be associated with spontaneous vaginal delivery in squirrel monkeys. However, pelvic support of the bladder was not protected by this intervention suggesting that effects of pregnancy and delivery are not uniformly prevented by this procedure.

Animal models for pelvic organ prolapse: systematic review

“…Of these, only parity was strongly correlated with the development of bladder descent (defined as 7 mm below the bony pelvis). The effects of pregnancy and delivery were studied in detail, using magnetic resonance imaging to assess the anatomy of the pelvic floor muscles and width of the bony pelvic outlet and measure bladder neck descent [ 9 , 64 ]. The muscles studied were the levator, obturator internus and coccygeus, which are all considered relevant to pelvic floor support.…”

“…The muscles studied were the levator, obturator internus and coccygeus, which are all considered relevant to pelvic floor support. In particular, the coccygeus muscle was directly affected by the passage of the fetal head during delivery [ 9 , 64 ]. Immediately postpartum, there is a reduction in levator and obturator internus volume, but this effect was similar following vaginal and abdominal delivery.…”

“…This would be indicative of tissue edema and hence be an indirect sign of trauma by passage of the head. At 3 to 4 months after delivery, no permanent anatomical changes are visible in the pelvic floor muscles anymore [ 9 , 64 ]. On the other hand, the bladder neck position is lower immediately after vaginal delivery and even more 3–4 months postpartum [ 9 , 64 ] .…”

“…At 3 to 4 months after delivery, no permanent anatomical changes are visible in the pelvic floor muscles anymore [ 9 , 64 ]. On the other hand, the bladder neck position is lower immediately after vaginal delivery and even more 3–4 months postpartum [ 9 , 64 ] . This was associated with an increase in the width of the pelvic outlet [ 64 ].…”

“…On the other hand, the bladder neck position is lower immediately after vaginal delivery and even more 3–4 months postpartum [ 9 , 64 ] . This was associated with an increase in the width of the pelvic outlet [ 64 ]. Remarkably, the extent of the descent and the width of the pelvic outlet were similar 3–4 months postpartum, whether delivery was vaginal or by cesarean section [ 64 ].…”