This randomized, single-blind controlled trial aims to evaluate the effects of maternal lullaby singing during infant bathing on mother-infant bonding, postpartum depressive symptoms, and perceived parenting self-efficacy in mothers of healthy term infants. The postpartum period represents a critical phase for maternal psychological adjustment, during which stress, depressive symptoms, and low parenting confidence may negatively affect the quality of mother-infant interaction and bonding. Low-cost, culturally meaningful, and non-pharmacological interventions that support maternal well-being and early bonding are therefore of particular importance.

The study will be conducted with mothers who have delivered healthy term infants in a public hospital. Eligible participants will be randomly assigned to either an intervention group or a control group. Mothers in the intervention group will receive a structured bathing education and will be instructed to bathe their infants three times per week for two consecutive weeks while singing a lullaby using their own voice in a calm and quiet home environment. Live-recorded music will not be used. The intervention emphasizes sensory interaction, emotional closeness, and maternal voice as key components. Each bathing session is expected to last approximately 10-15 minutes. The control group will receive routine postpartum care without a structured lullaby-based bathing intervention.

Outcome measures include mother-infant bonding, postpartum depressive symptoms, and perceived maternal parenting self-efficacy. Data will be collected at two time points: prior to hospital discharge (within the first 24 hours postpartum) and at the end of the two-week intervention period. Validated self-report instruments will be used for all outcome assessments.

The findings of this study are expected to provide evidence on the effectiveness of a simple, culturally embedded caregiving practice in supporting maternal mental health, strengthening mother-infant bonding, and enhancing parenting confidence during the early postpartum period. Results may inform postpartum care practices, parental counseling programs, and midwife-led supportive interventions.

Inclusion Criteria:

• Mothers who have had an uncomplicated pregnancy and delivery
• Mothers who are healthy enough to care for their baby
• Mothers who have suitable conditions at home to bathe their baby
• Babies born at term (≥ 37 weeks of gestation) and with stable general health after birth

Exclusion Criteria:

• Mothers with a history of serious postpartum complications (such as postpartum hemorrhage)
• Mothers diagnosed with psychiatric illness
• Mothers who are unable to participate directly in the care of their baby (due to severe disability, mandatory bed rest, etc.)
• Mothers who cannot participate in the lullaby program due to hearing impairment
• Infants who experience serious respiratory, cardiac, or neurological problems at birth or thereafter, who have a skin disease or dermatological condition that limits bathing, who have a history of admission to the neonatal intensive care unit, or who have a chronic disease or congenital anomaly