Purpose To investigate the correlation between cervical length measurements using transvaginal and transperineal approaches at 16‐24 weeks of gestation. Methods The prospective study recruited 110 singleton pregnant women. All the measurements were performed by one operator who was blinded to the results of both approaches. Cervical length was first measured by transvaginal sonography (TVUS) then transperineal sonography (TPUS). The transvaginal approach was used as the reference measurement. Patient preference regarding the sonographic approaches was evaluated using questionnaire. Results Cervical length was successfully measured by TVUS in all cases. TPUS was successful in 108/110 participants. There was high correlation between the results of TVUS and TPUS (Pearson's correlation coefficient was .94; 95% CI .9 to .95. Lin's concordance correlation coefficient was .94; 95% CI .92‐.96). The estimated difference in cervical length measured using TVUS and TPUS was .2 mm. The 95% tolerance interval for paired observation was −1.8 to 2.3 mm. The interobserver coefficient of TPUS measurement was .98 (95% CI .92‐.99). TPUS was rated as resulting in mild or no discomfort and was preferred by most women. Conclusion TVUS and TPUS techniques showed high correlation in cervical length measurement with high interobserver reliability. More patients preferred TPUS. TPUS should be considered as an alternative method of cervical length measurement.

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