Assessment of the variability in the dimensions of the intact pelvic canal in South Africans: A pilot study.

Cephalopelvic disproportion is common among Africans and is a major cause of maternal and perinatal mortality and morbidity. As the dimensions of the pelvis may vary between populations and according to stature and age, they need to be considered during childbirth and also in the planning and performance of pelvic and perineal procedures. The aim of this study was to assess the possible variations in the dimensions of the intact pelvic canal in South Africans and their implications. Eighty intact cadaver pelves, belonging to 40 white South Africans (20 males and 20 females) and 40 black South Africans (20 males and 20 females) were used for both metric and geometric morphometric analyses. Pelvic inlet shapes did not differ significantly between groups but pelvic inlet and midpelvic dimensions were the greatest in white South Africans and females. The pubic symphyseal length was the greatest in white males and the smallest in black females, resulting in a smaller pelvic cavity anteriorly than for white females. Pelvic outlet shapes varied significantly between sexes in white South Africans and between white and black males. Females presented with the greatest dimensions. Black South African females presented with an elongated anteroposterior outlet diameter. Certain transverse pelvic diameters correlated positively with age in white males and with height in females. In planning childbirth options, the smaller pelvic inlet of black females and stature-dependent diameters should be considered. Pelvic and perineal surgery may be technically more challenging because of smaller pelvic dimensions in black South Africans, especially in males.

Magnetic resonance imaging pelvimetry and the prediction of labor dystocia.

OBJECTIVE: To study whether magnetic resonance imaging (MRI) pelvimetry has the ability to identify those women who require cesarean delivery for labor dystocia. METHODS: From July 2003 to April 2004, nulliparous women scheduled for a labor induction for prolonged pregnancy (42 weeks) were asked to participate in a pelvimetry study. Those who consented underwent fast-acquisition MRI that included two 90-second acquisitions to evaluate fetal biometry and volumetry and maternal pelvimetry, including novel measurements of pelvic bony and soft tissue volumes as determined by MRI. Information about each patient's pregnancy, labor course, and neonatal outcome was prospectively collected. Pelvimetry results for those women undergoing operative delivery for labor dystocia were compared with those who did not. Single fetal and maternal pelvic measurements, as well as ratios of both, were analyzed. In addition, previously described radiographic pelvimetry techniques and formulas to predict dystocia were used. RESULTS: One hundred one women underwent MRI, and 22 of these underwent cesarean delivery for dystocia. No single fetal measurement was statistically associated with dystocia. Several maternal pelvic measures, fetal-to-maternal ratios, and previously reported pelvimetric techniques were significantly associated with dystocia. The ratio of magnetic resonance (MR) fetal head volume to pelvic soft tissue volume had statistical significance (P = .04). Receiver operator characteristic curves were developed for the different measurements, ratios, and formulas studied to assess whether any of the techniques could accurately predict labor dystocia requiring operative delivery. The area under the curve values ranged from 0.6 to 0.8, with the ratio of MR head volume to pelvic soft tissue being 0.7. These values suggest that MRI can identify those women at greatest risk for dystocia, but it cannot with accuracy predict which ones will require a cesarean. CONCLUSION: We found significant associations with MRI pelvimetry and labor dystocia, but MRI was not a significant improvement over previously described pelvimetric techniques. LEVEL OF EVIDENCE: II-3.