The capacity of mid-pregnancy cervical length to predict preterm birth in low-risk women: A national cohort study

Jeanine Van Der Ven, Melanie A. Van Os, Brenda M. Kazemier, Emily Kleinrouweler, Corine J. Verhoeven, Esteriek De Miranda, Aleid G. Van Wassenaer-Leemhuis, Petra N. Kuiper, Martina Porath, Christine Willekes, Mallory D. Woiski, Marko J. Sikkema, Frans J.M.E. Roumen, Patrick M. Bossuyt, Monique C. Haak, Christianne J.M. De Groot, Ben W.J. Mol, Eva Pajkrt

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Introduction. We investigated the predictive capacity of mid-trimester cervical length (CL) measurement for spontaneous and iatrogenic preterm birth. Material and methods. We performed a prospective observational cohort study in nulliparous women and low-risk multiparous women with a singleton pregnancy between 16+0 and 21+6 weeks of gestation. We assessed the prognostic capacity of transvaginally measured mid-trimester CL for spontaneous and iatrogenic preterm birth (<37 weeks) using likelihood ratios (LR) and receiver-operating-characteristic analysis. We calculated numbers needed to screen to prevent one preterm birth assuming different treatment effects. Main outcome measures were preterm birth <32, <34 and <37 weeks. Results. We studied 11 943 women, of whom 666 (5.6%) delivered preterm: 464 (3.9%) spontaneous and 202 (1.7%) iatrogenic. Mean CL was 44.1 mm (SD 7.8 mm). In nulliparous women, the LRs for spontaneous preterm birth varied between 27 (95% CI 7.7-95) for a CL ≤ 20 mm, and 2.0 (95% CI 1.6-2.5) for a CL between 30 and 35 mm. For low-risk multiparous women, these LRs were 37 (95% CI 7.5-182) and 1.5 (95% CI 0.97-2.2), respectively. Using a cut-off for CL ≤ 30 mm, 28 (6.0%) of 464 women with spontaneous preterm birth were identified. The number needed to screen to prevent one case of preterm birth was 618 in nulliparous women and 1417 for low-risk multiparous women (40% treatment effect, cut-off 30 mm). Conclusion. In women at low risk of preterm birth, CL predicts spontaneous preterm birth. However, its isolated use as a screening tool has limited value due to low sensitivity.

Original languageEnglish
Pages (from-to)1223-1234
Number of pages12
JournalActa Obstetricia et Gynecologica Scandinavica
Issue number11
Publication statusPublished - 1 Nov 2015
Externally publishedYes


  • Cervical length measurement
  • low-risk population
  • preterm birth

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