title: Cervical length at mid-pregnancy and the risk of primary cesarean delivery.
abstract: BACKGROUND
  Physiological and biochemical studies suggest that normal parturition at term is dependent on programmed development of the uterus in early pregnancy. It is recognized that a short cervix in mid-pregnancy is associated with an increased risk of spontaneous preterm birth. We hypothesized that a long cervix in mid-pregnancy would be associated with an increased risk of cesarean delivery during labor at term.
  
  
  METHODS
  We studied 27,472 primiparous women who had a cervical length of 16 mm or more at a median of 23 weeks of gestation and who ultimately delivered a live infant in labor at term.
  
  
  RESULTS
  The rate of cesarean delivery at term was lowest (16.0%) among women with a mid-pregnancy cervical length in the lowest quartile (16 to 30 mm) and was significantly greater in the second quartile (18.4%, 31 to 35 mm), third quartile (21.7%, 36 to 39 mm), and fourth quartile (25.7%, 40 to 67 mm) (P<0.001 for trend). The odds ratio for cesarean delivery among women in the fourth quartile, as compared with the first quartile, was 1.81 (95% confidence interval [CI], 1.66 to 1.97), and the odds ratio adjusted for maternal age, body-mass index, smoking status, race or ethnic group, gestational age at birth, spontaneous or induced labor, birth-weight percentile, and hospital of delivery was 1.68 (95% CI, 1.53 to 1.84; P<0.001). The increased risk of cesarean delivery was attributable to procedures performed for poor progress in labor.
  
  
  CONCLUSIONS
  The cervical length at mid-pregnancy is an independent predictor of the risk of cesarean delivery at term in primiparous women.
authors: Department of Obstetrics and Gynaecology, Cambridge University, Cambridge, United Kingdom. gcss2@cam.ac.uk
authors: Gordon C S
authors: GC
authors: Smith
authors: Ebru
authors: E
authors: Celik
authors: Meekai
authors: M
authors: To
authors: Olga
authors: O
authors: Khouri
authors: Kypros H
authors: KH
authors: Nicolaides
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D002584:Cervix Uteri / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D002585:Cesarean Section; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012306:Risk