Background. Dysbiotic conditions among pregnant women may lead to the translocation of opportunistic microorganisms into breast milk through the enteromammary pathway, thereby increasing the risk of lactostasis, mastitis, and neonatal gastrointestinal disorders. Administering probiotics during this critical period may be an effective preventive strategy.

Aim. To evaluate the impact of oral probiotics on the microbiota of breast milk, the incidence of lactation-related complications in new mothers, and the health status of newborns during the first six weeks of life.

Materials and methods. A prospective randomized study was conducted involving 80 pregnant women. Participants were divided into three groups: a control group (physiological vaginal pH 3.8–4.5, n = 25); subgroup 2A (pH > 4.5, received probiotics, n = 30); and subgroup 2B (pH > 4.5, received no probiotics, n = 25). A breast milk culture was performed during the early postpartum period, and the incidence of lactostasis, mastitis, and neonatal gastrointestinal symptoms and infectious complications was assessed.

Results. Pathogens in breast milk were identified in over half of the cases in the subgroup without probiotics, with Staphylococcus aureus being predominant. Other microorganisms, such as Streptococcus agalactiae, Escherichia coli, and Klebsiella pneumoniae, as well as microbial associations, were also isolated. In contrast, the frequency of pathogen detection was significantly lower in the probiotic-treated group, with no S. agalactiae or its associated forms isolated. Lactostasis and lactation mastitis, including purulent forms, were reported infrequently in both the probiotic and control groups. In the subgroup without probiotics, these complications occurred significantly more frequently. Moreover, newborns whose mothers received probiotics experienced fewer episodes of infantile colic and regurgitation, whereas severe enterocolitis was reported exclusively in infants from the group without probiotic support.

Conclusion. Administering oral probiotics to pregnant women with baseline vaginal pH > 4.5 aims to restore the intestinal microbiota. This improvement in intestinal microbiocenosis is associated with an indirect reduction in the frequency of pathogen detection in breast milk, a decreased occurrence of lactostasis and mastitis (including purulent forms) among new mothers, as well as a significant reduction in gastrointestinal symptoms (regurgitation and colic) in newborns, compared to those without probiotic intervention.