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Researchers discover the fetal autonomic system resilience

Researchers in Fairfax, VA discover the effects of various birthing modes on the fetal autonomic system

As expectant mothers prepare for the labors of childbirth, the only thing on their mind is how to birth a healthy and happy baby. During this time, the human body undergoes its own methods of preparing the fetus for the extra-uterine transition. Various hormonal changes, such as increased catecholamine levels, aid in regulating the baby’s breathing, heartbeat, blood pressure, and energy metabolism during delivery. In addition, the mother’s body aids in readying the brain and fetal autonomic system by adapting its cerebral connections for a life outside the womb. The autonomic system of the human body is a vital part of the nervous system as it ensures continual and unconscious regulation of bodily function.

Fortunately, due to society’s medical advancements, there are now numerous methods for fetal delivery. Published by Scientific Reports, researchers sought to understand the relationship between various modes of delivery and their effects on the fetal autonomic system development. A cohort study examined 118 low-risk newborns, born at the median age of 39.3 weeks. Each was grouped into three different categories: vaginal delivery, cesarean section after labor (in which the first birth was via vaginal delivery and the second via cesarean), and elective cesarean section. The following characteristics were also accounted for: gestational age, postnatal age, and percent active states. The autonomic function of the newborns was measured by the heart rate variability and gamma brain wave activity via cortical electroencephalogram activity. An increase in gamma activity indicated an increase in wakefulness and learning.

The study found that the mode of labor delivery did not significantly alter the fetal autonomic system tone. However, infants that were born by cesarean section, showed significantly increased heart rate accelerations after labor. Furthermore, infants born ultimately by cesarean section after an initial attempt at vaginal delivery had significantly lower EEG activity when compared to vaginal delivery or elective cesarean section.

According to the researchers, these results indicate an increased stress response from the newborns. It was concluded that babies who underwent more than a single mode of delivery may have had a combined stress of labor and abdominal delivery.

As being the first study of its kind, naturally, it had its own limitations. Firstly, there was a difference in the timing of the recordings between infant groups. Those born via cesarean section stayed in the hospital for 48 hours while vaginal deliveries were discharged within 24 hours. Secondly, the study faced a limited time in data collection due to the newborn’s clinical care (i.e., feedings). Lastly, there was a risk of insufficient quality data due to the infants being irritable and lacking consistent sleep and wakefulness sleep cycles.

Nonetheless, this study opens the door for a deeper understanding of the miraculous process of childbirth, suggesting the irrespective of vaginal delivery or c-section, the fetal autonomic nervous system does not suffer.

Written by Stephanie Tsang, BHSc


Mulkey, S. B., Kota, S., Govindan, R. B., Al-Shargabi, T., Swisher, C. B., Eze, A., . . . Plessis, A. J. (2019). The effect of labor and delivery mode on electrocortical and brainstem autonomic function during neonatal transition. Scientific Reports, 9(1). doi:10.1038/s41598-019-47306-1

Henderson, D. (2019, July 31). Autonomic nervous system appears to function well regardless of mode of childbirth. Retrieved from



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