Uterine contractions during labor and engagement in the birth canal can compress the fetal head. The impact on the fetus is unclear and still controversial. In this integrative physiological review we highlight evidence that decelerations are uncommonly associated with fetal head compression. Next, the fetus has an impressive ability to adapt to increased intracranial pressure through activation of the intracranial baroreflex, such that fetal cerebral perfusion is well maintained during labor except in the setting of prolonged systemic hypoxemia leading to secondary cardiovascular compromise. Thus, when it occurs fetal head compression is not necessarily benign but does not seem to be a common contributor to intrapartum decelerations. Finally, the intracranial baroreflex and the peripheral chemoreflex (the response to acute hypoxemia) have overlapping efferent effects. We propose the hypothesis that these reflexes may work synergistically to promote fetal adaptation to labor.

分娩过程中的子宫收缩和进入产道会压迫胎头。对胎儿的影响尚不清楚，且仍有争议。在这篇综合生理学综述中，我们强调了减速与胎头受压不常见相关的证据。其次，胎儿通过激活颅内压力反射具有令人印象深刻的适应颅内压升高的能力，使得胎儿脑灌注在分娩过程中得到良好维持，除非长期全身低氧血症导致继发性心血管损害。因此，当胎儿头部受压发生时，不一定是良性的，但似乎也不是产时减速的常见原因。最后，颅内压力反射和外周化学反射（对急性低氧血症的反应）具有重叠的传出效应。我们提出这样的假设：这些反射可能协同作用以促进胎儿对分娩的适应。