How Parental Stress Shapes a Baby’s Nervous System!

Research is helping us understand just how deeply a mothers psychological and physiological state is interconnected with their baby’s developing biology. 

Trauma does not exist in isolation; a mother’s childhood experiences can directly influence the calibration of their infant’s stress response system. A study from Federal University of São Paulo, Brazil, reveals the potential connection between a mother’s childhood experiences and her infant’s developing stress system. The study followed 305 mother-infant duos, measuring levels of the stress hormone cortisol in both mother and baby at one month and six months postpartum. The results showed that a mother’s and their baby’s cortisol levels are positively synchronized, especially during the early weeks of life. The correlation begins to weaken by six months, suggesting that the infant’s own stress-regulation system begins to mature and differentiate from the mother’s.1

A mother’s history of Adverse Childhood Experiences (ACEs) — such as physical, sexual, and psychological abuse, neglect, poverty, and parental mental illness — predicts elevated lifetime cortisol levels, which also persist through pregnancy, leading to an increased fetal exposure to stress.2 A mother who has endured significant stress as a child is more likely to have a dysregulated stress response as an adult. This dysregulation can manifest as elevated cortisol levels during the demanding postpartum period, and due to the synchronization of cortisol levels between mother and newborn, the infant’s own stress system could be influenced by this heightened hormonal state.1

This biological attunement is meant to be a source of co-regulation, however this can become maladaptive, such as when a mother struggles with anxiety (a common outcome of past trauma).3 One study showed that in home settings where parents and infant both wore sensors, their heart and arousal levels were synchronized.3 In less-anxious infant-parent dyads, the parent can act as a calming agent for the infant, whereas an anxious parent reacts to the infant’s minor fluctuations. This can lead to the infant’s nervous system having fewer chances to practice self-soothing, and leads to infant signs of chronic stress: feeding intolerance, erratic sleep-wake cycles, and pervasive difficulty achieving calm alertness.3

Additionally, periods of parental anxiety (elevated heart rate, cortisol) may correlate with infant signs of dysregulation (such as feeding intolerance, erratic sleep-wake cycles, difficulty achieving calm alertness). For example, infants of parents with anxiety disorders showed consistently elevated heart rate, a core sign of sympathetic nervous system arousal and autonomic dysregulation.3

We can now understand that the parent-infant bond is a biological co-regulatory relationship and that parental stress/anxiety is not confined to the parent but can affect infants’ developing stress responses. 

The physiological connection between mother and infant can also directly counteract the aforementioned cycles of dysregulation. The most effective tool is proximity-based, regulated touch, such as Kangaroo Care (KC) and Skin-to-Skin Contact (SSC). Proximity-based touch stabilizes cardiorespiratory function in infants (e.g., heart rate, respiration rate, oxygen saturation).  The effect is especially pronounced and beneficial for preterm and at-risk newborns, as preemies often have immature self-regulatory systems, and proximity-based touch helps to compensate for this.4

Additionally, we must shift the clinical model for truly supportive care within the NICU and other perinatal support settings from an infant-focused approach to a dyad-focused approach. This means recognizing the parent as an essential component in their infant’s care, whose own well-being is foundational to the infant’s developmental outcomes.

REFERENCES

  1. Ramos, A. C., Cogo-Moreira, H., Eid, M., Santana, V. O., Ribeiro, L. P., Milani, A. C. C., Silva, I., Duarte, C. S., Posner, J., & Jackowski, A. P. (2025). Mother infant cortisol levels and maternal childhood adversity. Scientific reports, 15(1), 44746. https://doi.org/10.1038/s41598-025-28548-8
  2. Moog, N. K. et al. Maternal exposure to childhood trauma is associated during pregnancy with placental-fetal stress physiology. Biol. Psychiatry79, 831–839 (2016). [DOI] [PMC free article] [PubMed] [Google Scholar][Ref list]
  3. Smith, C. G., Jones, E. J. H., Charman, T., Clackson, K., Mirza, F. U., & Wass, S. V. (2022). Anxious parents show higher physiological synchrony with their infants. Psychological medicine, 52(14), 3040–3050. https://doi.org/10.1017/S0033291720005085
  4. de Vente, W., Majdandžić, M., & Bögels, S. M. (2020). Intergenerational transmission of anxiety: linking parental anxiety to infant autonomic hyperarousal and fearful temperament. Journal of child psychology and psychiatry, and allied disciplines, 61(11), 1203–1212. https://doi.org/10.1111/jcpp.13208
  5. Valori, I., Merkel, J. L., Furlan, G., Grossmann, T., & Fairhurst, M. T. (2025). Touch facilitates newborns’ self-regulation: Systematic review of multidimensional arousal outcomes. Neuroscience and biobehavioral reviews, 178, 106353. https://doi.org/10.1016/j.neubiorev.2025.106353