What does four-dimensional head mean?

In general, there are three positions of the fetal presentation during pregnancy, one is the cephalic position, and the other is the breech position. The cephalic position is that the fetal head is above the pelvis, the breech position is that the fetal buttocks, or the feet are above the pelvis. The transverse position refers to that the fetal pelvis is empty. At this time, the fetus is transverse to the uterus. In this case, it is called transverse position. Under normal circumstances, most of the cephalic position can be delivered naturally, while breech position and transverse position require caesarean section.