Tabriz University of Medical Sciences Health Promotion Perspectives 2228-6497 16 2 2026 08 21 Effect of Maternal Probiotic Supplementation During Breastfeeding on Postpartum Depression and Bilirubin Levels in Low-Birth-Weight (1000–2000 G) Infants: A Randomized Controlled Trial 272 281 10.34172/hpp.45313 EN Maryam Alikamali https://orcid.org/0000-0002-7064-4165 Mahnaz Shahnazi Mojgan Mirghafourvand Manizheh Mostafa-Gharehbaghi Aziz Homayouni-Rad Zahra Fardiazar Sakineh Mohammad-Alizadeh-Charandabi https://orcid.org/0000-0003-4785-9333 Journal Article 10.34172/hpp.45313 2025 10 12 2026 02 16 Introduction: Evidence on the effects of maternal probiotic supplementation on postpartum mental health and neonatal outcomes in low birth weight infants remains limited. This study examined whether postpartum maternal oral supplementation with Lactobacillus paracasei 431 and Bifidobacterium lactis BB-12 (1×10⁹ CFU/day each) alleviates postpartum depression (PPD) symptoms and reduces total serum bilirubin (TSB) levels in infants weighing 1000–2000 g at birth (two primary outcomes). Methods: In this randomized, double-blind, placebo-controlled trial, women who had delivered within 48 hours and intended to breastfeed their infants received either probiotics or placebo for 42–45 days. Mothers—not infants—were the unit of randomization (stratified by twin status and birth-weight category). Postpartum depression was assessed using the Edinburgh Postnatal Depression Scale at baseline and at 42–45 days postpartum. TSB was assessed at baseline and on days 4 and 7 of the intervention. ANCOVA and repeated measures ANOVA, adjusted for baseline values and the stratification factors were used to compare the groups in terms of PPD score and TSB levels, respectively. Results: One hundred twenty-two mothers (138 infants, including 16 sets of twins) were enrolled and randomized into two groups. After one mother dropped per group, data from 60 mothers and 69 infants in each group were analyzed. Depression scores did not differ significantly between the probiotic and placebo groups (adjusted mean difference −1.6; 95% confidence interval [CI] −3.9 to 0.69). Similarly, infant TSB levels across days 4 and 7 of the intervention showed no significant differences (0.21; 95% CI: −0.31 to 0.73). One infant death and two cases of positive blood culture occurred in each group. Conclusion: The maternal probiotic supplementation during breastfeeding in mothers of infants weighing 1000–2000 g at birth did not significantly affect postpartum depression or infant TSB levels. Any potential benefit of higher probiotic doses or longer intervention periods remains speculative and should be weighed against neonatal safety considerations. Trial registration: IRCT20100414003706N42 (registered 22 November 2022, revised 4 February 2024; https://en.irct.ir/trial/65451).