Evaluation of sonographic assessment of the progress of labor

To evaluate the practical application of intrapartum sonographic assessment of the progress of labor.

Eighty three full-term pregnant women who delivered at the Obstetrics and Gynecology Department were enrolled into this study. Transperineal ultrasonographic examinations were conducted with a convex transducer at the onset of active labor, yielding mid-sagittal and coronal images. Three parameters were measured: 1) the angle between the long axis of the symphysis pubis and the line joining its lowest margin to the contour of the fetal head (angle of progression); 2) the distance between the presenting point and the line perpendicular to the symphysis pubis and passing through its lowest margin; 3) the fetal head-perineum distance. The relationship between measurement results and the period from examination to delivery was also analyzed.

There were 73 vaginal deliveries and 10 women underwent a cesarean section due to failure to progress. The two groups (vaginal vs. cesarean delivery) differed significantly in terms of the angle of progression (131 vs. 110 degrees, respectively p<0.01) and the distance between the presenting point and the infrapubic line (34 vs. 20 mm, respectively p<0.01). The inter-group difference in fetal head-peritoneum distances (53 and 61 mm, respectively) was noticeable but non-significant (p>0.05). The study also demonstrated a relationship between all three of the measured values and the time to second labor phase completion.

Ultrasonography may be useful in assessing the progress of labor as well as in predicting or early diagnosis of abnormal fetal head descent.