Objective: To evaluate the practical application of intrapartum sonographic assessment of the progress of labor.
Material and methods: 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.
Results: 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.
Conclusions: Ultrasonography may be useful in assessing the progress of labor as well as in predicting or early diagnosis of abnormal fetal head descent.