title: Obstetric risk factors for umbilical cord prolapse: a nationwide population-based study in Japan.
abstract: To demonstrate the clinical course and the obstetric risk factors for umbilical cord prolapse.
  
  
  
  The clinical course of reported cases of umbilical cord prolapse that occurred in Japan between 2007 and 2011 was retrospectively analyzed. The obstetric risk factors for umbilical cord prolapse were investigated by a nationwide population-based case-cohort study.
  
  
  
  Three hundred and sixty-nine cases (0.018 %) of fore-lying/prolapsed umbilical cord in 2,037,460 deliveries were analyzed. Most cases of fore-lying umbilical cord were diagnosed by an ultrasound scan (78 %), whereas umbilical cord prolapse was most frequently diagnosed by an internal examination (63 %). Umbilical cord prolapse was found to be significantly associated with the following factors: multiple pregnancy [odds ratio (OR) 3.57; 95 % confidence interval (CI) 2.60, 4.90], non-vertex presentation (OR 4.67; 95 %CI 3.73, 5.86), preterm labor (OR 2.28; 95 %CI 1.83, 2.83), premature rupture of membranes (OR 3.84; 95 %CI 3.10, 4.77), prolapsed amniotic bag (OR 12.31; 95 %CI 9.00, 16.85), polyhydramnios (OR 2.89; 95 %CI 1.49, 5.61), and a birth weight of <2500 g (OR 2.26; 95 %CI 1.84, 2.79).
  
  
  
  The current study is the largest in Japan to demonstrate the obstetric clinical course and risk factors associated with umbilical cord prolapse. Prolapsed amniotic bag, labor and rupture of membrane during premature period, and fetal abnormal presentation induced by multiple pregnancy, and polyhydramnios were high risk situation for umbilical cord prolapse.
authors.affiliation: Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kanagawa, Japan. hasejun@oak.dti.ne.jp.
authors.forename: Junichi
authors.initials: J
authors.lastname: Hasegawa
authors.affiliation: Department of Obstetrics and Gynecology, Mie University School of Medicine, Mie, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Sekizawa
authors.affiliation: Ishiwata Obstetrics and Gynecology Hospital, Ibaraki, Japan.
authors.forename: Isamu
authors.initials: I
authors.lastname: Ishiwata
authors.affiliation: Seijo-Kinoshita Hospital, Tokyo, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kinoshita
mesh_terms: D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007744:Obstetric Labor Complications / Q000209:etiology*; D011247:Pregnancy; D011391:Prolapse; D012189:Retrospective Studies; D012307:Risk Factors; D014470:Umbilical Cord
keywords: Cervical balloon; Cord presentation; Emergency Cesarean section; Fetal death; Fetal heart rate tracing; Fore-lying cord; Non-reassuring fetal status; Pregnancy complication; Umbilical cord prolapse