title: Ultrasound Assessment of Abdominal Muscle Thickness in Postpartum vs Nulliparous Women.
abstract: OBJECTIVE
  The purpose of this study was to determine the effect size in measurable change of abdominal musculature morphology using ultrasonography in postpartum women within 1 month of a healthy, vaginal delivery.
  
  
  METHODS
  One hundred fifty-six participants were recruited for this study. B-mode ultrasound imaging was used to measure abdominal muscle thickness on 80 nulliparous women and 76 mothers who had delivered within the past 4 weeks. Measures were taken for the upper and lower rectus abdominus, external and internal obliques, and transversus abdominus at rest.
  
  
  RESULTS
  Statistically significant differences were found in the thickness of the rectus abdominus muscle at both sites; upper (P < .0001) and lower (P < .0001) as well as the internal oblique (P < .0001). All 3 muscles were thinner in postpartum participants (8.29 ± 1.83 mm, 8.89 ± 2.29 mm, and 7.06 ± 1.82 mm, respectively) within the first month of delivery than in controls (10.82 ± 1.93 mm, 11.13 ± 2.38 mm, and 8.36 ± 1.87 mm, respectively). Large effect sizes were found for the influence of pregnancy on the rectus muscle segments (1.35 for the upper rectus abdominus and 1.00 for the lower rectus abdominus) and a medium effect size for the internal oblique (0.71). No significant differences were observed in the remaining 2 muscles.
  
  
  CONCLUSIONS
  This study showed that there are differences in morphology of the abdominal muscles in pregnant women vs nonpregnant controls. The large effect sizes reported may provide the basis for future studies examining relationships between morphology, functional change, and back pain during pregnancy.
authors.affiliation: Chiropractor, Researcher, Department of Research, Canadian Memorial Chiropractic College, Toronto, Ontario, Canada. Electronic address: cweis@cmcc.ca.
authors.forename: Carol Ann
authors.initials: CA
authors.lastname: Weis
authors.affiliation: Professor, Graduate Education and Research Department, Canadian Memorial Chiropractic College, Toronto, Ontario, Canada.
authors.forename: John J
authors.initials: JJ
authors.lastname: Triano
authors.affiliation: Chief of Maternal Fetal Medicine Program, Maternal Fetal Medicine and Program Research Director of Womens and Babies, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Jon
authors.initials: J
authors.lastname: Barrett
authors.affiliation: Chiropractor, Private Practice, London, Ontario, Canada.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Campbell
authors.affiliation: Chiropractor, Private Practice, Hamilton, Ontario, Canada.
authors.forename: Martine
authors.initials: M
authors.lastname: Croy
authors.affiliation: Chiropractor, Private Practice, Toronto, Ontario, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Roeder
mesh_terms: D000009:Abdominal Muscles / Q000502:physiology* / Q000648:ultrastructure*; D000328:Adult; D005260:Female; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D010298:Parity; D017773:Pelvic Floor / Q000502:physiology; D049590:Postpartum Period; D017568:Rectus Abdominis / Q000000981:diagnostic imaging / Q000648:ultrastructure; D012016:Reference Values; D014463:Ultrasonography; D055815:Young Adult
keywords: Abdominal Muscles; Back Pain; Postpartum Period; Pregnancy; Ultrasonography