[Contracted pelvis determined from a three-dimensional viewpoint--2 step X-ray pelvimetry].

The definition of contracted pelvis set down by the Terminology Committee, Japan Society of Obstetrics and Gynecology concerns only the pelvic inlet. We maintain, however, that contracted pelvis in Japanese women should be considered from a three-dimensional viewpoint. It can be easily defined by the area of the pelvic inlet and the sacral shape. In the present study, the following results were obtained after extracting 108 sets of superior-interior and lateral pelviographs. 1) When the area of the pelvic inlet is > or = 110 cm 2, the possibility of contracted pelvis can be excluded. 2) When the area is < 100 cm2, the incidence of c/s is quite high; this condition should therefore be termed contracted pelvis. 3) Subjects with inlet areas of 100-110 cm2 are classified as "relative contracted pelvis" and account for about one third of the total number of patients. It is only in this group that lateral pelviographies should be taken. When it reveals the presence of sacral deformity, c/s is necessary in 1/2 of the cases, and vaginal deliveries can be expected in 95% without sacrum deformity. When a given pelvis is categorized as "normal" according to the definition, the c/s rate is as high as 50% in cases with a deformed sacrum, but when the sacrum is not deformed, the rate is as low as 25%, 4) The above technique consists of two steps: (a) First, a superior-inferior pelviography is taken to measure the inlet area to discriminate the high-risk group.(ABSTRACT TRUNCATED AT 250 WORDS)