The shape and size of pelvis vary from person to person, which can be divided into four types: female pelvis: the three planes of pelvis are wide and the side walls are not adhered, which is suitable for fetal delivery. This type accounts for 1/2 of female pelvis in China.

Male pelvis: the upper part of the pelvis is triangular, the transverse diameter of the middle pelvis and outlet is small, and the pelvic side wall has cohesion. If the diameter is very small, dystocia is easy to occur, and this kind of pelvis accounts for 1%~3.7% of women in China.

Ape pelvis: The anteroposterior diameter of each plane of the pelvis is larger than the transverse diameter, the bones can be tilted backwards, the side walls are cohesive, and the pelvis is deep. This kind of pelvis accounts for 1/6~ 1/7 of women in China.

Flat pelvis: shallow pelvis, short anteroposterior diameter, and backward cabin bone. Simple flat pelvis, as long as the fetal head can enter the pelvic entrance, other diameters are relatively plentiful. This kind of pelvis accounts for 1/3~ 1/4 of women in China.

The pelvis is mostly mixed, and the simple pelvis is less.

In short, no matter what pelvic type, as long as the fetal head is commensurate with the pelvis, vaginal delivery can be achieved.