A LONGITUDINAL-STUDY OF THE CERVIX IN PREGNANCY USING TRANSVAGINAL ULTRASOUND

Objective To study longitudinal changes in the cervix during pregnancy using transvaginal ultrasound and secondly, to determine whether the measures used change with gestational age, and whether there are diffe rences between nulliparous and primiparous women. Design A longitudina l study involving five transvaginal ultrasound examinations of each wo man at specified gestational ages from 18 to 30 weeks. Participants Tw enty-one nulliparous and 20 primiparous women completed the study and were delivered at term. Cervical length, diameter and dilatation were assessed at each examination. Results In both nulliparous and primipar ous women there is no significant change in either cervical length or diameter over the time period studied. In primiparous women the cervix is significantly longer than in nulliparous women (44.4 (5.1)mm vel s us 40.6 (4.7) mm [mean (SD)]; P < 0.001). The cervical diameter in pri miparous women is also significantly greater (31.8 (4.0) mm versus 29. 0 (3.7)mm; P < 0.01). Conclusions Cervical length and diameter are con stant in both nulliparous and primiparous women throughout this gestat ional period. The cervix in primiparous women is both longer and thick er than in nulliparous women.