[Echotomographic aspects of cervical incompetence during pregnancy].

During pregnancy, the opening of the cervix can be measured by perineal echotomography. Among 200 per-gravidic clinical echotomographies, 23 cervical incompetences were recognized. A "funnel-shaped" cervix is a cervix with an internal os larger than the external os; thus no clinical sign may be apparent and only a supra-vaginal Shirodkar's operation should be done.