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Am J Perinatol 2023; 40(02): 187-193
DOI: 10.1055/s-0041-1728818
Original Article

Midtrimester Cervical Length in Low-Risk Nulliparous Women for the Prediction of Spontaneous Preterm Birth: Should We Consider a New Definition of Short Cervix?

Paul Guerby 
1   Research Center, CHU de Québec-Université Laval, Québec, Canada
,
Mario Girard
1   Research Center, CHU de Québec-Université Laval, Québec, Canada
,
Geneviève Marcoux
1   Research Center, CHU de Québec-Université Laval, Québec, Canada
,
Annie Beaudoin
1   Research Center, CHU de Québec-Université Laval, Québec, Canada
,
Jean-Charles Pasquier
2   Department of Obstetrics and Gynecology, Université de Sherbrooke, Faculté de Médecine et des Sciences de la Santé 3001, Sherbrooke, Quebec, Canada
,
Emmanuel Bujold 
1   Research Center, CHU de Québec-Université Laval, Québec, Canada
3   Department of Obstetrics and Gynecology, Faculty of Medicine, Université Laval, Québec, Canada
› Author Affiliations
Funding This study was supported by the Jeanne and Jean-Louis Levesque Perinatal Research Chair at Université Laval, Québec, Canada. Prof. E.B. holds a Clinician Scientist award from Fonds de recherche du Québec–Santé (FRQS), Québec, Canada. P.G. holds a postdoctoral Award from the FRQS and INSERM (Institut National de la Santé et de la Recherche Médicale).
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Abstract

Objective The study aimed to estimate the predictive value of midtrimester cervical length (CL) and the optimal cut-off of CL that should be applied with asymptomatic nulliparous women for the prediction of spontaneous preterm birth (sPTB).

Study Design This is a prospective cohort study of asymptomatic nulliparous women with a singleton gestation. Participants underwent CL measurement by transvaginal ultrasound between 20 and 24 weeks of gestation. The participants and their health care providers remained blinded to the results of CL measurement. The primary outcomes were sPTB before 35 weeks and sPTB before 37 weeks. Receiver operating characteristics (ROC) curve analyses were performed. Analyses were repeated by using multiples of median (MoM) of CL adjusted for gestational age.

Results Of 796 participants, the mean midtrimester CL was 40 ± 6 mm with a 1st, 5th, and 10th percentile of 25, 29, and 32 mm, respectively. ROC curve analyses suggest that a cut-off of 30 mm was the optimal CL to predict sPTB before 35 weeks (area under the ROC curve [AUC]: 0.70, 95% confidence interval [CI]: 0.56–0.85) and before 37 weeks (AUC: 0.70, 95% CI: 0.59–0.80). Midtrimester CL <30 mm could detect 35% of all sPTB before 35 weeks at a false-positive rate of 5% (relative risk: 9.1, 95% CI: 3.5–23.5, p < 0.001). We observed similar results using a cut-off of CL <0.75 MoM adjusted for gestational age.

Conclusion A midtrimester CL cut-off of 30 mm (instead of 25 mm), or CL less than 0.75 MoM, should be used to identify nulliparous women at high risk of sPTB.

Key Points

  • The optimal CL cut-off for the prediction of sPTB is 30 mm in nulliparous women.

  • In nulliparous women, a midtrimester CL < 30 mm is highly associated with sPTB before 35 and 37 weeks.

  • A midtrimester of CL <30 mm (5th percentile) should define a short cervix in asymptomatic nulliparous women.

Keywords

cervical length - short cervix - screening - preterm birth - nulliparous


Publication History

Received: 18 June 2020

Accepted: 02 March 2021

Article published online:
03 May 2021

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