UMR CNRS-Muséum National d'Histoire Naturelle, Paris, France.
Am J Phys Anthropol. 2011 Jul;145(3):438-45. doi: 10.1002/ajpa.21521. Epub 2011 May 3.
The developing fetus is protected from external environmental influences by maternal tissues. However, these structures have a limited elasticity, such that the fetus must grow in a confined space, constraining its size at the end of pregnancy. Can these constraints modify the morphology of the fetal skeleton? The intensity of these constraints increases between 5 months and birth, making it the most appropriate period to address this question. A sample of 89 fetal femora was analyzed, and results provide evidence that during this period, the torsion of the femoral shaft (quantified by means of a new three-dimensional method) increases gradually. Two explanations were considered: this increase could signal effects of constraints induced by the intrauterine cavity, developmental patterning, or some combination of these two. Different arguments tend to support the biomechanical explanation, rather than a programming pattern formation. Indeed, the identification of the femur as a first degree lever, created by the hyperflexion of the fetal lower limbs on the pelvis, could explain the increase in femoral shaft torsion during prenatal life. A comparison with femora of infants is in accordance with this mechanical interpretation, which is possible through bone modeling/remodeling. Although genetic and epigenetic mechanisms may regulate timing of fetal development, our data suggest that at birth, the fetal skeleton also has an intrauterine mechanical history through adaptive bone plasticity.
发育中的胎儿受到母体组织的保护，免受外界环境的影响。然而，这些结构的弹性有限，因此胎儿必须在有限的空间内生长，从而限制了其在妊娠末期的大小。这些限制会改变胎儿骨骼的形态吗？这些限制在 5 个月到出生期间逐渐增强，因此这是解决这个问题的最佳时期。我们分析了 89 根胎儿股骨，结果表明，在此期间，股骨骨干的扭转（通过一种新的三维方法来量化）逐渐增加。有两种解释：这种增加可能表明了由子宫腔引起的约束、发育模式或这两者的某种组合的影响。不同的论点倾向于支持生物力学解释，而不是编程模式形成。事实上，将胎儿下肢在骨盆上的过度弯曲定义为一个第一级杠杆，就可以解释在产前生活中股骨骨干扭转的增加。与婴儿的股骨进行比较符合这种机械解释，这是通过骨骼的重塑来实现的。尽管遗传和表观遗传机制可能调节胎儿发育的时间，但我们的数据表明，在出生时，胎儿骨骼也通过适应性骨骼可塑性具有宫内机械史。
