Association Between Early Postpartum Maternal Fatigue and Infant Emotional Development: Protocol for a Prospective Cohort Study

Postpartum fatigue (PPF) is clinically defined as persistent physical and mental exhaustion emerging after childbirth that cannot be fully relieved by rest. It is distinct from postpartum depression and has a prevalence of 76.13% among Chinese women within the first postpartum week. Existing evidence suggests that maternal PPF may alter salivary oxytocin concentrations, disturb maternal caregiving behaviors, and subsequently interfere with multiple dimensions of infant emotional development, including emotional expression, emotional regulation, and emotional recognition. Objective psychophysiological measurements, such as eye-tracking and galvanic skin response, have been validated for assessing infant emotional responses. Nevertheless, most existing studies focus merely on maternal mental well-being. Local longitudinal evidence clarifying this sequential mechanistic chain remains limited, and targeted early screening and intervention strategies for PPF-affected mother-infant dyads are insufficient.

This prospective cohort protocol aims to examine the independent association between maternal PPF and the emotional development of 3-month-old infants and to explore the sequential mediating roles of salivary oxytocin and mother-infant caregiving quality. The primary hypothesis is that higher PPF severity will correlate with poorer infant emotional development outcomes. The secondary hypothesis is that oxytocin levels and maternal caregiving sequentially mediate this association.

We will recruit 412 mother-infant dyads with maternal PPF within 1 week postpartum. PPF severity will be measured by the Postpartum Fatigue Scale. Infant emotional development, covering expression, regulation, and recognition, will be evaluated via questionnaires and physiological assessments, including eye-tracking and galvanic skin response, at an infant age of 3 months. General analytical frameworks will be applied for hypothesis testing.

This study was funded and initiated in September 2025. Participant recruitment commenced in October 2025. A total of 180 mothers-infants dyads underwent eligibility screening; 146 of these dyads completed enrollment, yielding a participation rate of 81.1%. Twelve dyads withdrew before the 3-month follow-up window, and 4 dyads were lost to follow-up at the 3-month assessment. To date, 112 dyads have completed the full 3-month postpartum assessment, and the remaining participants are still under follow-up. No major protocol deviations have occurred. Data analysis of samples from participants who have completed the 3-month assessments is ongoing. According to the prespecified timeline, full sample collection is projected to be completed by December 2027, and formal data analysis will begin shortly thereafter. The study is progressing steadily in accordance with preset schedules. Full dataset analysis and submission of the final manuscript are anticipated in early 2028.

This cohort will generate longitudinal evidence describing links between maternal PPF and early infant emotional development in Chinese postpartum populations. The findings may help identify high-risk mother-infant subgroups and provide real-world evidence to develop targeted early screening and dyadic support strategies for postpartum mothers and their infants.