title: Association between second-trimester cervical length and cesarean delivery in multiparas.
abstract: OBJECTIVE
  The purpose of this study was to determine whether there is an association between second-trimester cervical length and cesarean delivery in women with a prior vaginal delivery.
  
  
  METHODS
  We conducted a retrospective cohort study of multiparous women with singleton gestations who underwent routine cervical length screening between 18 and 24 weeks' gestation and labored after 34 weeks. Cervical lengths were divided into quartiles, and the frequency of cesarean delivery was compared across the groups. Indications for cesarean delivery were also compared. A multivariable logistic regression was performed with cervical length as a categorical and a continuous variable to adjust for potential confounders.
  
  
  RESULTS
  Of the 2260 multiparas who met inclusion criteria, 63 (2.8%) underwent a cesarean delivery. We observed no association between the second-trimester cervical length quartile and the frequency of cesarean delivery (2.1%, 3.5%, 2.3%, and 3.1%, respectively; P = .434). Further analysis using cervical length as a continuous variable and controlling for potential confounding variables did not change this result (adjusted odds ratio, 1.08; 95% confidence interval, 0.80-1.46).
  
  
  CONCLUSIONS
  The second-trimester cervical length quartile in multiparas is not associated with an increased frequency of cesarean delivery. This finding differs from studies of nulliparas.
authors.affiliation: From Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA. Revision requested January 20, 2014. emily-miller-1@fsm.northwestern.edu.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Miller
authors.affiliation: From Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA. Revision requested January 20, 2014.
authors.forename: Brett
authors.initials: B
authors.lastname: Einerson
authors.affiliation: From Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA. Revision requested January 20, 2014.
authors.forename: Sadia
authors.initials: S
authors.lastname: Sahabi
authors.affiliation: From Northwestern University, Feinberg School of Medicine, Chicago, Illinois USA. Revision requested January 20, 2014.
authors.forename: William A
authors.initials: WA
authors.lastname: Grobman
mesh_terms: D000328:Adult; D001724:Birth Weight; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D002585:Cesarean Section; D005260:Female; D005865:Gestational Age; D006801:Humans; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D012189:Retrospective Studies; D012307:Risk Factors; D016216:Ultrasonography, Prenatal
keywords: cervical length; cesarean delivery; obstetric ultrasound; obstetrics; transvaginal sonograph