Maternal physiological stress peaks during newborn sleep, finds relief during breastfeeding in primiparous women.

Postpartum stress (PPS) significantly impacts maternal-infant health, contributing to adverse outcomes like preterm birth and low birthweight. Despite the known risks, the dynamic association between specific newborn behavioral states and maternal physiological stress during rooming-in remains poorly understood. Current postpartum care often emphasizes maternal rest when the infant sleeps, yet this may not align with the mother's actual physiological stress response. Understanding these real-time physiological shifts, particularly in autonomic activity, is crucial for developing more effective and supportive postpartum care strategies.

This prospective repeated-measures observational study enrolled 43 healthy, full-term, primiparous women after vaginal birth, accompanied by a partner, at a hospital in Taiwan. Participants with clinical complications or cardiac arrhythmias were excluded. Maternal normalized low frequency (nLF), a measure of sympathetic nervous system activity, was continuously monitored via portable ECG across four distinct newborn states: crying, breastfeeding, being held, and sleeping. A subgroup of 30 mothers provided complete newborn state diaries and continuous ECG data for synchronized analysis. Data were analyzed using descriptive statistics, paired samples t-tests, and correlation tests to assess associations.

Overall maternal nLF significantly increased from Day 1 (T1) to Day 3 (T2) postpartum (p=0.022, N=43), indicating a general rise in physiological stress during early hospitalization. No significant associations were observed between nLF and rooming-in levels (p>0.05, n=30), suggesting that the level of rooming-in alone did not dictate stress responses. Contrary to expectations, a substantial 73% of participants experienced their highest level of maternal physiological stress while the infant slept, with an average nLF of 65.4%. This finding suggests a state of situational alertness rather than rest during infant sleep. Conversely, breastfeeding demonstrated a distinct stress-relieving potential:

40% of participants exhibited their lowest stress levels during breastfeeding, with an average nLF of 60.2%, highlighting its calming effect on the maternal autonomic nervous system. These results provide preliminary evidence that maternal autonomic activity varies considerably across different caregiving contexts.