Cervical length at mid-pregnancy and the risk of primary cesarean delivery

N Engl J Med. 2008 Mar 27;358(13):1346-53. doi: 10.1056/NEJMoa0706834.


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.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cervical Length Measurement*
  • Cervix Uteri / anatomy & histology*
  • Cervix Uteri / diagnostic imaging
  • Cesarean Section*
  • Female
  • Gestational Age
  • Humans
  • Infant, Newborn
  • Logistic Models
  • Pregnancy
  • Pregnancy Trimester, Second
  • Risk