[Expression of sexual dimorphism in the fetal pelvic girdle]

The objective of this study was to analyse the development of the foetal pelvis in order to define normal anatomic reference values as a function of gender and gestational age. The study population included 500 stillborn foetuses between the gestational ages of 18 and 41 weeks. Those foetuses without known demographic histories were strictly excluded. For each case studied, an AP radiograph was performed with the following parameters measured by two independent observers: pelvic width, inter-iliac width, inter-sciatic nodes, inter-pubic width and bi-ischial width. The correlation between these radiographic measurements and the gestational age as well as the gender was analysed. The result indicated that the inter-ischiatic distance is significantly greater in the female foetus after the 26-27th week of gestation (P < 0.0062). Standard growth for the female and the male foetal pelvis is proposed with potential application in the study of normal and pathological development of the foetus.