The uterocervical angle is the triangular segment measured between the lower uterine segment and the cervical canal, yielding a measurable angle. The first ray was placed from the internal os to the external os. The calipers were placed where the anterior and posterior walls of the cervix touch the internal and external os along the endocervical canal. If the cervix was curved, the first ray was also drawn from the internal os to the external os as a straight line. A second ray was then drawn to delineate the lower uterine segment. This ray was traced up the anterior uterine segment to a distance allowed by the preloaded image. Ideally, the second ray would reach 3cm up the lower uterine segment in order to establish an adequate measurement. The anterior angle in between the two rays was measured with a protractor. In the presence of funneling, the first ray was placed to measure the length of remaining cervix. The second caliper was placed from the innermost portion of measurable cervix and extended to the lower uterine segment. In the event that the lower uterine segment was found to be irregular, the second caliper was placed centrally along the segment. In the event of a retroverted uterus, the angle should be measured in a similar fashion with the first ray along the measurable cervix and the second ray traced along the lower uterine segment. Unlike in an anteverted or axial positioned uterus, however, the posterior side of the angle closer to the intrauterine contents should then be measured.
To determine whether a novel ultrasonographic marker, uterocervical angle, correlates with risk of spontaneous preterm birth