Prediction of preterm birth: the accuracy of transvaginal cervical length measurement in the second trimester ultrasound

Abstract

Preterm birth (PTB) is a major public health problem with a big impact on infantile morbidity and mortality. Therefore, PTB risk assessment is essential so that treatment can be taken out as a preventive measure. Transvaginal ultrasound measurement of the cervical length (TUCL) has been proposed and adopted as an effective method for PTB screening. Purpose: To assess the second-trimester TUCL applicability and effectiveness in predicting PTB among Portuguese pregnant women. Methods: An observational retrospective cohort study was conducted including all singleton pregnant women who presented for second-trimester ultrasound at Centro Hospitalar Universitário de São João, delivered at the same institution and had TUCL according to the Fetal Medicine Foundation guidelines. Results: 6433 women were included in our cohort. Spontaneous PTB accounted for 3.5%, with 0.7% classified as early PTB (<34th week of gestation). The mean TUCL was 34.03mm ± 4.78mm. TUCL ≤25mm sensitivity was 9.3%, specificity 97.6%, area under the curve 0.53, negative predictive value 96.7% and positive predictive value 12.5%. A negative association between TUCL and PTB was showed in the multiple logistic regression analysis, with an odds ratio (OR) of 0.91 (95% confidence interval [95%CI]: 0.89-0.94; p<0.001). For our cohort, the best TUCL cut-off was 20mm. Conclusion: Our study confirmed that TUCL is a valuable tool, especially in identifying women with low-risk PTB. However, an integrative risk assessment model should be performed to improve the screening algorithm. Additionally, for risk stratification improvement, it highlights the importance of adopting population-specific cut-offs.