Cervical length and internal cervical os dilatation evaluated by two-dimensional and three-dimensional ultrasound

Purpose: to compare the uterine cervix measurements and funneling obtained by two-and three-dimensional transvaginal sonography during pregnancy. Methods: a prospective, descriptive study, with group comparison, was carried out between April 2004 and February 2005 in 74 pregnant women, who were between the 19th and 24th week of pregnancy, regardless of risk factors for premature delivery. The ultrasound examination of the cervix was carried out only once in the same patient and by only one observer. The measurements of the cervix by two-dimensional ultrasound were made at the time of the test and by three-dimensional ultrasound at intervals of 7 to 15 days after the two-dimensional ultrasound. The measurements of cervical length, funnel width and length were taken by two-dimensional ultrasound in the sagittal plane and by three-dimensional in the sagittal plane as well as in coronal plane. Results: there was no significant difference between the averages of the measurements of the cervix obtained by two-and three-dimensional ultrasound in the sagittal plane (p=0.23); however, there was a difference in the averages of the measurements of the cervix obtained by two-dimensional ultrasound in sagittal plane and three-dimensional ultrasound in the coronal plane (p=0.009) and between three-dimensional ultrasound in the sagittal and coronal planes (p=0.001). The kappa test (0.86) showed no superiority of either the two-dimensional and three-dimensional ultrasound in the visualization of the cervical funnel. No statistically significant difference was observed between the methods when the average of the measurements of funneling was compared (p>0.05). Conclusion: there were differences between two-dimensional and three-dimensional ultrasound of cervical length, only using the coronal plane of the three-dimensional ultrasound.