Cervical length vs VOCAL cervical volume for predicting pre-term delivery in asymptomatic women at 20-22 weeks' pregnancy.

We conducted a prospective observational study of 306 asymptomatic women at 20-22 weeks of pregnancy to compare 3-dimensional ultrasound measurements of cervical volume with 2-dimensional ultrasound measurements of cervical length to evaluate the performance of cervical volume as a predictor of pre-term delivery, compared with the current standard, cervical length. Participants underwent transvaginal ultrasound measurements of cervical length (mm) and cervical volume (cm(3)). Cervical volume as measured by 3-dimensional ultrasound was found to be a useful tool for predicting pre-term delivery; however, due to the high correlation between cervical length and cervical volume and the lack of differences in the sensitivity, specificity, positive predictive value, negative predictive value and relative risk between the two methods, replacing cervical length measurements with cervical volume calculations does not seem to be justified for this purpose, because of increased difficulty in volume acquisition.