[Research on the progress of the fetal head in the occipito-posterior position]

We have studied by means of B type ultrasound, the fetal positions and their progress in 221 cases, among which 117 were serially observed. The results showed a marked increase in the incidence of occipito-posterior position (OP) after onset of labor and marked decrease of occipito-anterior position (OA). The antepartum fetal position was influenced mainly by placental site but during labor also by the type and size of the pelvis. The incidence of OP after onset of labor was 33.03% of which 53.13% could rotate spontaneously to anterior position and be delivered as such but 29.69% remained as persistent occipito-posterior position (POP). We also discussed about the differences in the duration and types of deliveries in OP as determined by different labor processes as well as the relationship between the different labor processes and the three major factors affecting labor, particularly in occiput left posterior and occiput right posterior positions.