title: Maternal adaptations in preparation for parturition predict uncomplicated spontaneous delivery outcome.
abstract: OBJECTIVE
  The objective of the study was to define maternal tissue adaptations in pregnancy associated with uncomplicated spontaneous vaginal delivery using anatomical and biological outcomes.
  
  
  METHODS
  Nulliparous gravidas were prospectively enrolled in the first trimester at 2 institutions. Demographic and delivery data were chart abstracted. Vaginal elastase activity (units per milligram of protein) and Pelvic Organ Prolapse Quantification measurements of pelvic organ support were obtained in the first and third trimesters. A subset underwent 3-dimensional ultrasound measures of levator hiatus. Uncomplicated spontaneous vaginal delivery (VD) was defined as no cesarean, forceps, vacuum, shoulder dystocia, third- or fourth-degree perineal laceration, or prolonged second stage labor.
  
  
  RESULTS
  We enrolled 173 women in their first trimester, 50 of whom had ultrasounds. Mean age was 25.5 ± 5.5 years with a body mass index of 28.0 ± 7.3 kg/m(2). Sixty-seven percent were white/Caucasian, 27% black/African American, and 6% Hispanic/Latina. Mean delivery gestational age was 38.5 ± 2.9 weeks, with 23% delivering by cesarean and 59% achieving uncomplicated spontaneous VD. Vaginal support changed significantly over trimesters with posterior vaginal and hiatal relaxation, vaginal lengthening, and increased levator hiatus area during strain. Women achieving uncomplicated spontaneous VD demonstrated significantly greater relaxation on third-trimester Pelvic Organ Prolapse Quantification for anterior, apical, and hiatal measures than those without uncomplicated spontaneous VD. Higher first-trimester vaginal elastase activity was strongly associated with uncomplicated spontaneous VD (geometric mean activity 0.289 ± 0.830 U/mg vs -0.029 ± 0.585 U/mg, P = .009). Higher first-trimester elastase, younger age, lower first-trimester body mass index, and more third-trimester vaginal support laxity in points C and GH were predictive of VD success.
  
  
  CONCLUSIONS
  Significant maternal adaptations occur in the vagina during pregnancy, presumably in preparation for vaginal delivery. Greater adaptation, including vaginal descent and higher first-trimester elastase activity, is associated with an increased likelihood of uncomplicated spontaneous VD.
authors.affiliation: Division of Urogynecology, Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR.
authors.forename: Sallie S
authors.initials: SS
authors.lastname: Oliphant
authors.affiliation: Division of Urogynecology, Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City, UT.
authors.forename: Ingrid E
authors.initials: IE
authors.lastname: Nygaard
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Sciences, and Magee-Womens Research Institute and Foundation, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zong
authors.affiliation: Division of Ultrasonography, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA.
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Canavan
authors.affiliation: Division of Urogynecology and Reconstructive Pelvic Surgery, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA; Department of Obstetrics, Gynecology, and Reproductive Sciences, and Magee-Womens Research Institute and Foundation, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA.
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Moalli
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data; D036861:Delivery, Obstetric / Q000706:statistics & numerical data*; D005113:Extraction, Obstetrical / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D010196:Pancreatic Elastase / Q000378:metabolism; D036801:Parturition / Q000502:physiology*; D017773:Pelvic Floor / Q000000981:diagnostic imaging / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D011261:Pregnancy Trimester, First; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D014463:Ultrasonography; D014621:Vagina / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology*; D055815:Young Adult
chemical_list: D010196:Pancreatic Elastase
keywords: childbirth; delivery; elastase; maternal adaptations; pelvic organ prolapse