The normal value of the inter-iliac spine diameter is 23-26 centimeters. The size of the pelvis and its shape have a direct impact on labor and delivery, and are important factors in determining whether the fetus can be delivered vaginally smoothly. Therefore, pelvic measurement should be done during the prenatal checkup, and pelvic measurement is divided into two types: external measurement and internal measurement. The external measurement of the pelvis can indirectly determine the size and shape of the pelvis, and the operation is relatively simple, in which the iliac spine diameter belongs to the external measurement of the pelvis. During the measurement, the pregnant woman is asked to lie on her back with her legs stretched out, and the distance between the outer edges of the two anterior superior iliac spines is measured.