title: Randomized trial of cesarean vs vaginal delivery for effects on the pelvic floor in squirrel monkeys.
abstract: BACKGROUND
  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 humanlike pattern of spontaneous age- and parity-associated pelvic organ prolapse.
  
  
  OBJECTIVE
  The potential to prevent or diminish these changes with scheduled cesarean delivery (CD) has not been evaluated. In a randomized, controlled trial, we compared female squirrel monkeys undergoing spontaneous vaginal delivery with those undergoing scheduled primary CD for pelvic floor muscle volumes, muscle contrast changes, and dynamic effects on bladder neck position.
  
  
  METHODS
  Levator ani, obturator internus, and coccygeus (COC) 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 postpartum. The position of bladder neck relative to bony reference line also was assessed with abdominal pressure using dynamic magnetic resonance imaging.
  
  
  RESULTS
  Baseline measurements of 10 females randomly assigned to scheduled primary CD 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 < .05) in the observation immediately after pregnancy. The COC muscles increased (P < .05) immediately after delivery for females in the spontaneous vaginal delivery group, but not for females in the scheduled CD group. Position of the bladder neck descended (P < .05) by 3 months postpartum in both groups.
  
  
  CONCLUSIONS
  Scheduled CD diminishes changes in COC 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.
authors.affiliation: Department of Obstetrics and Gynecology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX. Electronic address: FionaLindoMD@gmail.com.
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Lindo
authors.affiliation: Department of Obstetrics and Gynecology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Carr
authors.affiliation: Department of Obstetrics and Gynecology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX.
authors.forename: Michelle
authors.initials: M
authors.lastname: Reyes
authors.affiliation: Department of Radiology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX.
authors.forename: Jilene M
authors.initials: JM
authors.lastname: Gendron
authors.affiliation: Department of Veterinary Sciences, Michale E. Keeling Center for Comparative Medicine and Research, University of Texas MD Anderson Cancer Center, Bastrop, TX.
authors.forename: Julio C
authors.initials: JC
authors.lastname: Ruiz
authors.affiliation: Department of Veterinary Sciences, Michale E. Keeling Center for Comparative Medicine and Research, University of Texas MD Anderson Cancer Center, Bastrop, TX.
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Parks
authors.affiliation: Department of Obstetrics and Gynecology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX; Department of Pediatrics, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX; Department of Molecular and Cellular Medicine, Radiology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX; Department of Veterinary Sciences, Michale E. Keeling Center for Comparative Medicine and Research, University of Texas MD Anderson Cancer Center, Bastrop, TX.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Kuehl
authors.affiliation: Department of Obstetrics and Gynecology, Scott and White Healthcare, and Texas A&M Health Science Center College of Medicine, Temple, TX.
authors.forename: Wilma I
authors.initials: WI
authors.lastname: Larsen
mesh_terms: D000818:Animals; D002585:Cesarean Section; D036861:Delivery, Obstetric; D005260:Female; D008279:Magnetic Resonance Imaging; D053580:Muscle Strength; D009130:Muscle, Smooth / Q000033:anatomy & histology*; D017773:Pelvic Floor / Q000033:anatomy & histology*; D011897:Random Allocation; D012453:Saimiri
keywords: cesarean delivery; magnetic resonance imaging; pelvic floor muscles; pregnancy; squirrel monkey; vaginal delivery