OP09.09: Volumetric measurements of the cervix by 3D ultrasonography do not improve the prediction of preterm delivery when compared to cervical length measured by 2D ultrasonography

Abstract

The purpose of this study was to compare the diagnostic performance of cervical measurements by two-dimensional (2DUS) and three-dimensional ultrasonography (3DUS) for the prediction of early spontaneous preterm delivery (< 32 weeks). Ninety-one singleton asymptomatic pregnancies at risk for preterm delivery (history of spontaneous preterm delivery, conization, cervical insufficiency, or a cervical length < 25 mm in the second trimester) were examined by transvaginal ultrasonography between 22 and 24 weeks of gestation. Following cervical length measurement by 2DUS, a 3DUS volume dataset was acquired using the sagittal acquisition plane. Volumes were retrospectively examined offline by an examiner blinded to the results of the 2DUS examination. Cervical length was measured in the sagittal plane displayed with the multiplanar technique. Cervical volume measurements were obtained by three techniques: 1) VOCAL™; 2) a manual segmentation technique consisting of cutting with the electronic scalpel along the contours of the cervix on multiplanar display; and 3) calculation based on the ellipsoid formula. ROC curves for each parameter were calculated and measures of diagnostic efficiency to predict spontaneous preterm delivery < 32 weeks were determined. Fifteen patients were excluded because they had indicated preterm delivery. The frequency of early spontaneous preterm delivery was 17.1% (13/76). All parameters were significantly associated with an increased risk of preterm delivery before 32 weeks. However, no difference in diagnostic efficiency was observed when cervical length measurements by 2DUS were compared to cervical length or volumetric measurements by 3DUS (see Table). Cervical length or volumetric measurements of the uterine cervix by three-dimensional ultrasound did not improve the prediction of early spontaneous preterm delivery over that of cervical length obtained by two-dimensional ultrasound.