Until now, studies of birth physiology among humans were based on interpretations of difficulties. Textbooks have extensively reproduced comparative drawings of maternal pelvis and fetal head to explain the particularities of childbirth in our species. This is why the importance of mechanical factors has been overestimated by theoreticians. Instead of focusing on difficulties, we should first interpret the well-known fact that, occasionally, women who are not special from a morphological perspective can give birth easily and quickly, while others need medical intervention after days of hard labor. This enormous discrepancy is providing reasons to include birth physiology in the framework of brain physiology. This article aims to interpret some of the physiological maternal changes in late pregnancy.