Objectives To develop normal reference ranges for cervical volume and vascular indices using threedimensional (3D) power [17][18][19][20][21][22][23][24][25][26][27][28][29][30] P < 0.0001; median VFI 1.6 vs. 0.9, P < 0.0001

Objectives

Objectives To create reference values representative of normal findings on two-dimensional (2D) and three-dimensional (3D) transvaginal ultrasound (TVS) examination of the cervix from 17 to 41 weeks' gestation and to determine the agreement between cervical measurements taken by 2D and 3D TVS. Methods results was expressed as the mean (± 2 SDs) difference between the results of the two methods and as the interclass correlation coefficient (inter-CC).Results There was excellent agreement between measurements taken by 3.9 (range, 1.0-6.1) cm, 3.0 (range, 0.4-5.7) cm and 0.8 (range, 0.4-3.4 17-30 weeks to 3.5 (range, 1.8-5.5) cm at 31-40 weeks and to 4.0 (range, 2.8-5.9) cm at 41 weeks. Cervical width was 3.7 (range, 2.3-6.0) cm at 17-30 weeks and 4.5 (range, 2.3-6.1) ) cm (results obtained by 3D ultrasound). Cervical AP diameter and width did not differ between nulliparous and parous women. Median AP diameter increased from 3.0 (range, 2.0-4.6) cm at