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Previous Volume 358:1346-1353 March 27, 2008 Number 13 Next

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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.

Source Information

From the Department of Obstetrics and Gynaecology, Cambridge University, Cambridge, United Kingdom (G.C.S.S.); and the Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London (E.C., M.T., O.K., K.H.N.).

Address reprint requests to Dr. Smith at the Department of Obstetrics and Gynaecology, Cambridge University, Box 223, Rosie Maternity Hospital, Cambridge CB2 2SW, United Kingdom, or at gcss2{at}cam.ac.uk.

Full Text of this Article

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