Objective:The aim of this study of multifetal pregnancies was the comparison of three-dimensional (3D) volumetry of the cervix, conventional sonographic cervical length measurement and clinical assessment. Methods 10 mothers were investigated in an observational study between 5/1999 and 9/2000. A total of 34 consecutive 2D-and 3D-transabdominal ultrasound measurements were performed. Results: Volumetry of the cervix was possible in all 34 exams. 2D-cervical length assessment could not be obtained in 6% because the presenting fetal part obstructed the sonographic plane. Both methods allowed equal judgement of the configuration of the cervix. A significant correlation was found between mean 2D-cervical length (28.7 mm, 7.7 SD) and mean cervical volume (30.0 cm(3), 16.0 SD). Parity, subjective preterm labor or need of tocolytics showed no correlation with any biometrical parameter studied. Conclusion: Volumetry was superior for the assessment of cervical biometry and conformation in women when the transabdominal 2D-plane was obstructed. When cervical length was obtainable by a conventional scan, the technically more complex 3D-imaging did not provide further information. Copyright (C) 2001 S. Karger AG, Basel.