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Article Dans Une Revue American Journal of Human Biology Année : 2021

Pelvic and neonatal size correlations in light of evolutionary hypotheses

Les corrélations entre la taille pelvienne et neonatale à la lumière des hypothèses évolutives

Résumé

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.
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Dates et versions

hal-03443032 , version 1 (23-11-2021)

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Pierre Frémondière, Lionel Thollon, François Marchal. Pelvic and neonatal size correlations in light of evolutionary hypotheses. American Journal of Human Biology, 2021, ⟨10.1002/ajhb.23619⟩. ⟨hal-03443032⟩
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