The aim of this study is to assess influence of probiotic Lactobacillus reuteri DSM 17938 on formation of gut microbiota in infant born by Caesarean section. It is anticipated that daily using of probiotic Lactobacillus reuteri DSM 17938 can prevent development of early dysbiosis of gut microbiota induced by Caesarean section.

This is a single-center prospective randomized double-blind placebo-controlled clinical study. The planned duration of the study for each included infant will be 16 weeks, 4 weeks of study drug intake and 12 weeks of follow-up. 140 healthy infants born by Caesarean section will be included in the general group of the study, and 60 healthy infants born by natural vaginal delivery will be included in the control group. For infants included in the control group, all the same protocol requirements and procedures will be applied as for infants in the general group, except for randomization and the study product / placebo intake. Infants included in the general study group will be randomly assigned into the study product / placebo subgroups in 1: 1 ratio. During the study the gut microbiota will be analyzed. Feces samples should be collected no later than 72 hours after birth, and also on 14th day of life ± 3 days, 30th day of life ± 3 days and 112th day of life ± 3 days. Short-chain fatty acids (SCFA) will be analyzed in feces samples.

Inclusion Criteria:

• gestational age more than 37 weeks and less than 41 weeks
• age of enrolment is not more than 48 hours
• birth weight is corresponded to gestational age
• Apgar score ≥8 at 5 minutes
• Absence of congenital anomaly and/or clinical or physical abnormalities identified during clinical examination
• Primarily breastfeeding during the first days of life (more than 50%)
• Parent(s) are willing to comply with the exclusive breastfeeding regime during study period
• Parent(s) are willing to follow dietary recommendations during study period
• Parent(s) are willing to fill in the Diary every day
• Availability of the parent(s) and the infant during study period
• Written informed consent of the parent(s)

Exclusion Criteria:

• Chronic diseases or serious health problems of mother or child
• Gastrointestinal tract diseases of mother or child
• Delay in development
• Congenital abnormalities
• Intake of antibiotics by mother orally and / or vaginally during the last trimester of pregnancy
• Intake of probiotics by mother during the last trimester of pregnancy
• Using of general anesthesia during Caesarean section
• Emergency Caesarean section