A Comparison of Cervical Ruler and Transvaginal Ultrasound for Cervical Length Measurement during Pregnancy

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Warinya Jearranaikarn
Teera Siwadune


Objective: To identify and compare the correlation between cervical length measured by transvaginal ultrasound and cervical ruler.

Materials and Methods: A cross-sectional study was conducted in 200 singleton pregnant women who received antenatal care at Chonburi Hospital during September 1, 2018 to June 30, 2019. Transvaginal ultrasound and Cervical ruler for cervical measurement were performed during 16 to 24 weeks of gestation.  Maternal age, parity, pre-pregnancy weight, pre-pregnancy body mass index, history of abortion, history of preterm birth, smoking behavior, alcohol drinking and drug used during pregnancy were collected. Pearson’s Correlation Coefficient and paired T-test were used to evaluate the correlation and difference between cervical lengths measured by transvaginal ultrasound and cervical ruler.

Results: A total of 200 singleton pregnant women participated in the study. The average cervical length measured by transvaginal ultrasound and cervical ruler were 3.92 ± 0.71 cm. and 3.4 ± 0.73 cm., respectively. The mean difference of both methods was 0.52 cm. (95% confidence interval 0.46 to 0.57, P-value < 0.001). The correlation coefficient of cervical length measured by transvaginal ultrasound and cervical ruler was 0.843.

Conclusion: The cervical length measured by cervical ruler was correlated with the cervical length measured by transvaginal ultrasound; however, the average cervical length measured by cervical ruler was statistically significantly lower than those measured by transvaginal ultrasound.


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