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Observational Study
. 2015 Nov;94(11):1223-34.
doi: 10.1111/aogs.12721. Epub 2015 Sep 18.

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

Jeanine van der Ven  1 , Melanie A van Os  2 , Brenda M Kazemier  1 , Emily Kleinrouweler  1 , Corine J Verhoeven  3   4 , Esteriek de Miranda  1 , Aleid G van Wassenaer-Leemhuis  5 , Petra N Kuiper  6 , Martina Porath  3 , Christine Willekes  7 , Mallory D Woiski  8 , Marko J Sikkema  9 , Frans J M E Roumen  10 , Patrick M Bossuyt  11 , Monique C Haak  12 , Christianne J M de Groot  2 , Ben W J Mol  13 , Eva Pajkrt  1
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Free article
Observational Study

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

Jeanine van der Ven et al. Acta Obstet Gynecol Scand. 2015 Nov.
Free article

Abstract

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.

Keywords: Cervical length measurement; low-risk population; preterm birth.

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