Objective: To assess the variables useful to predict caesarean delivery (CD) and instrumental assistance, through the analysis of a large number of foetal-pelvic variables, using discriminant analysis. Materials and Methods: One hundred and fourteen pregnant women were included in this single-centre prospective study. For each mother-foetus pair, 43 pelvic and 18 foetal variables were measured. Partial least squares-discriminant analysis was performed to identify foetal-pelvic variables that could statistically separate the 3 delivery modality groups: spontaneous vaginal delivery (SVD), CD, and instrument-assisted delivery (IAD). Results: For the SVD versus CD model, voluminous foetuses and women with a narrow pelvic inlet had a greater risk for requiring CD. The most efficient variables for discrimination were the transverse diameter and foetal weight. The antero-posterior inlet and obstetric conjugate were considered in this model, with the former being a useful variable but not the latter. For the SVD versus IAD model, the most important variables were the foetal variables, particularly the bi-parietal diameter. Women with a reduced antero-posterior outlet diameter and a narrow pubic arch were more at risk of requiring an IAD. Conclusion: The antero-posterior inlet was an efficient variable unlike the obstetric conjugate. The obstetric conjugate diameter should no longer be considered a useful variable in estimating the arrest of labour. Antero-posterior inlet diameter was a sagittal variable that should be taken into account. The comparison of sub-pubic angle and bi-parietal and antero-posterior outlet diameters was useful in identifying a risk of requiring instrumental assistance.

Objective: To assess the variables useful to predict right-rotational birth (ROA) and left-rotational birth (LOA), through the analysis of a large number of foetalpelvic variables, using discriminant analysis. Materials and methods:One hundred and two pregnant women were included in this single centre prospective study. For each mother-foetus pair, 43 pelvic and 18 foetal variables were measured. Partial least squares-discriminant analysis was performed to identify foetal-pelvic variables that could statistically separate the 3 delivery modality groups: non-rotational birth or occiput anterior (OA), right-rotational birth and left-rotational birth.Results: For the OA versus LOA model, the most efficient variable for discrimination was the inlet-mid-plane angle. For the OA versus ROA model, the most important variable was the sacral overhang. For both model, we found that women with small foetuses, anthropoïd inlet, reduce posterior space of the mid-plane and reduce oulet were more likely to have non-rotational birth. Conclusion:This analysis helps us in identifying foetal-pelvic conditions to the rotation in physiological cases. It should be relevant to perform a similar work with cases of posterior position during explusion stage.

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization.

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Objective: The aim of this study was to analyse the correlations between maternal size, neonatal size, the dimensions of the maternal pelvis and gestational variables.Methods: In this study 131 mother-infant pairs were recruited. We investigate correlation between maternal traits (height, BMI, uterus height), neonatal traits (gestational age, birthweight, head, suboccipito-brematic and abdominal girth) and pelvic variables (conjugate diameter, inter-spinous diameter, sub-pubic angle) collected from computed tomography pelvimetry.Results: We found that the five neonatal traits are significantly inter-correlated. Among maternal traits, height is highly correlated with conjugate and inter-spinous diameters. Subpubic angle is correlated with inter-spinous diameter. Uterus height is correlated with the four neonatal growth traits. Gestational age is correlated with birthweight, head and abdominal girth. Among neonatal and pelvimetry correlations, conjugate diameter is highly correlated with suboccipito-bregmatic girth.Discussion: Matches between gestational age and neonatal traits, and between uterus height and neonatal traits could be related to the process of fetal maturation, orchestrated by the pregnancy clocks. Indeed, the triggering of parturition is supposed to result from the coordination and initiation of 4 clocks (endocrine, fetal membrane, decidual and myometrial) implying fetal organ maturation and fetal membrane senescence. Obstetric dilemma is an evolutionary tradeoff resulting from the conflicting pressures between bipedal locomotion efficiency and the selection for bigger brain size at birth. Correlation between suboccipito-bregmatic girth and conjugate suggests that the more the inlet is sagitally reduced, the smaller suboccipito-bregmatic girth is. Moreover, acquisition of the adult birth canal morphology causes minimal variation at the inlet, compare to the fetus morphology, suggesting that suboccipito-bregmatic girth follows the size of the inlet, but in one-way. Therefore, our interpretation of this pelvic-fetal correlation suggests that the pelvic size seems to be also a constraint to the fetal growth process. This adjustement of fetus size to the birth canal dimensions limits the risk of dystocia and could be interpretated as a remnant signature of the obstetric dilemma in our obstetrical sample.