Background and objective

During vaginal delivery, several positions can be adopted by the mother to be more comfortable and to help the labor process. The positions chosen are very influenced by factors such as monitoring and intervention during the second stage of labor. However, there is limited evidence to support the most ideal birthing position. This work aims at contributing to a better knowledge associated with the widening of the pubic symphysis and the biomechanics of flexible and non-flexible sacrum positions that can be adopted during the second stage of labor, as well as their resulting pathophysiological consequences.

Methods

A validated computational model composed by the pelvic floor muscles attached to the bones, and a fetus head was used to simulate vaginal deliveries. This model was modified to mimic two birthing positions: one that allows the free movement of the coccyx as in flexible sacrum positions and other in which this movement is more restricted as in non-flexible sacrum positions. The widening of the pubic symphysis was also considered to facilitate the passage of the fetus head.

Results

The results obtained showed that, in non-flexible sacrum positions, where the coccyx movement is restricted, occur a rotation of 3.6° of the coccyx and a widening of 6 mm of the pubic symphysis. In contrast, in flexible sacrum positions, where the coccyx is free to move, occur a rotation of 15.7° of the coccyx and a widening of the pubic symphysis of 3 mm, appearing to be more beneficial for the mother's pelvis, but slightly higher stresses were detected in the pelvic floor muscles.

Conclusions

Globally, the results obtained allow to conclude that different birthing positions lead to changes in the female pelvic space, so certain positions can be adopted by the mother during the second stage of labor to reduce the risk of obstructed labor and the development of several dysfunctions. More specifically, flexible sacrum positions, such as kneeling, standing, squatting and sitting positions, are more beneficial for the bone structure of her pelvis as they allow a higher coccyx movement and lower widening of the pubic symphysis.

中文翻译：

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从生物力学角度看分娩位置对其进化的影响

背景和目标

在阴道分娩过程中，母亲可以采用多个位置，以使其更舒适并有助于分娩。所选择的职位受第二产程中的监视和干预等因素影响很大。但是，仅有有限的证据支持最理想的分娩位置。这项工作的目的是有助于更好地了解与耻骨联合的扩大以及在第二产程中可以采用的灵活和不灵活的ac骨位置的生物力学相关的知识，以及由此产生的病理生理后果。

方法

经过验证的计算模型由附着在骨头上的骨盆底肌肉和胎儿头组成，用于模拟阴道分娩。对该模型进行了修改，以模仿两个分娩位置：一个允许尾骨自由移动，如在灵活的ac骨位置；另一种方式则使该运动受到更多限制，如非灵活的ac骨位置。耻骨联合的扩大也被认为有利于胎儿头的通过。

结果

获得的结果表明，在non骨运动受限的非骨位置，发生了3.6度的尾骨旋转和6 mm的耻骨联合增宽。相反，在尾骨可自由移动的flexible骨灵活位置，尾骨旋转15.7°，耻骨联合扩大3 mm，这似乎对母亲的骨盆更有利，但应力稍高在盆底肌肉中被发现。

结论

从全球来看，所获得的结果可以得出结论，不同的分娩位置会导致女性骨盆空间发生变化，因此母亲在第二个分娩阶段可以采取某些位置，以减少分娩受阻的风险和一些功能障碍的发生。更具体地说，灵活的s骨位置（如跪姿，站立，下蹲和坐姿）对她的骨盆的骨骼结构更有利，因为它们允许较高的尾骨运动和较低的耻骨联合宽度。