[Role of the cervix uteri at labor onset from ultrasound studies].

The cervix uteri is of greatest importance for the environment of the fetus. The sonographic imaging of the cervix uteri can be done by transabdominal, perineal and transvaginal route. Each of these methods are associated with specific advantages and disadvantages. During the time of gestation the cervix uteri can be measured sonographically concerning the length, the thickness, the width of the cervical canal and in addition the diameter of the internal and the external os. At the beginning of labour the cervix shows a transformation: a shortening with an increase of thickness. The phase of contraction is followed by a phase of reformation. Individual formations of the cervix regarding the a premature opening of the internal os or the external os could be demonstrable without clinical symptoms. By W. Eppel a score-like formula "Incompetence-Factor" was described for a quantification of these measurements.