Authors' objectives: Background: Preterm birth (PTB) is the leading cause of perinatal mortality and is associated with physical and mental impairments that may be lifelong. Prevention of PTB is therefore a high priority. Measurement of cervical length by vaginal ultrasound during the second trimester of pregnancy can be used for risk stratification since short cervical length is associated with an increased risk for PTB. Treatment with vaginal progesterone can reduce the risk for PTB and is a logical choice of treatment of asymptomatic women identified with short cervical length in a screening situation due to low invasiveness, high tolerability, low cost and evidence for efficacy. However, it is unclear if universal screening of pregnant women for short cervical length and subsequent treatment with vaginal progesterone, with or without additional treatment, is effective to prevent PTB. Question at issue: Is universal cervical length screening during the second trimester using vaginal ultrasound in women with singleton pregnancies, followed by vaginal or oral progesterone, with or without additional treatment, when short cervix length is demonstrated, effective in preventing any or spontaneous PTB and does it affect perinatal outcomes?

Authors' results and conclusions: Results: Two RCTs and four retrospective cohort studies with a total of 1,634 and 425,735 individuals, respectively, were included. The main problems in the two RCTs were imprecision due to low statistical power. In addition, one of the RCTs had problems with directness due to an unclear selection process and the study being performed in a health care setting that is substantially different from Sweden (India). Three cohort studies compared rates of PTB and perinatal outcomes before and after introduction of a screening program either in a geographical area or in a defined group of hospitals. One cohort study used a propensity score matched comparison of one institution that introduced screening with another that continued without screening. The high number of participants was a major strength of the cohort studies. Risk of bias, related to nonrandomised study design and use of historical controls, was the most important reason for reducing the level of certainty of evidence. Meta-analyses of the RCTs did not show any statistically significant association between cervical length screening and the rate of any or spontaneous PTB at any studied cut-off for gestational length. Meta-analyses of cohort studies showed a significant reduction of the risk for any and spontaneous PTB at <37 weeks; any PTB adjusted odds ratio 0.87 (95% confidence interval (CI) 0.78 to 0.98) and spontaneous PTB risk ratio (RR) 0.82 (95% CI 0.70 to 0.96), at <34 weeks; any PTB RR 0.85 (95% CI 0.74 to 0.97) and spontaneous PTB RR 0.77 (95% CI 0.66 to 0.90), and at <32 weeks; any PTB RR 0.84 (95% CI 0.74 to 0.99) and spontaneous PTB RR 0.68 (95% CI 0.49 to 0.95), but no statistically significant associations for any or spontaneous PTB at <30, <28 or <24 weeks. For perinatal mortality and morbidity, information was available in the RCTs only. No association between cervical length screening and perinatal mortality or morbidity was observed. Conclusion: Based on very low certainty of evidence, it is uncertain whether universal cervical length screening with vaginal ultrasound, followed by progesterone, with or without additional treatment, for women with short cervix and a singleton pregnancy, reduces the rate of any or spontaneous PTB, or affect perinatal outcomes, compared with no screening (GRADE ⊕ΟΟΟ). This conclusion is based on the absence of significant findings in severely underpowered RCTs. Although, meta-analyses of cohort studies showed statistically significant associations between cervical length screening, followed by treatment, to women with short cervix, and reduction of spontaneous PTB rates at <37, <34 and <32 weeks, this did not change the general conclusion due to concerns related to directness and risk of bias in these studies.

Authors' methods: Methods: Systematic literature searches were conducted in Medline, Embase, and the Cochrane Library. Titles, abstracts, and subsequently full text articles were independently screened by at least two authors. Final inclusion was decided in consensus amongst all authors. Included studies were critically appraised using checklists. The results of each study were summarised per outcome and, when possible, data were pooled in metaanalyses. The certainty of evidence was assessed using the GRADE approach.

Project Status: Completed

Year Published: 2025

URL for published report: https://mellanarkiv-offentlig.vgregion.se/alfresco/s/archive/stream/public/v1/source/available/sofia/su4372-2081313122-153/native/2025_141%20HTA-rapport%20Cervical%20length%20screening%20%20to%20prevent%20preterm%20birth%202025-06-02.pdf

English language abstract: An English language summary is available

Publication Type: Full HTA

Organisation Name: The Regional Health Technology Assessment Centre

Contact Address: The Regional Health Technology Assessment Centre, Region Vastra Gotaland, HTA-centrum, Roda Straket 8, Sahlgrenska Universitetssjukhuset, 413 45 GOTHENBORG, Sweden

Contact Name: hta-centrum@vgregion.se

Contact Email: hta-centrum@vgregion.se