Promotion of a healthy gut microbiome in elective caesarean section arrivals (PROMESA) by supplementing breastfed newborns with an infant probiotic.

INTERVENTION: Approximately 70 women will be recruited to provide vaginal and rectal swabs for baseline assessment of the maternal microbiome prior to Caesarean section. Newborn infants will be randomised to receive either a daily probiotic supplement (Bifidobacterium longum subsp. infantis EVC001 ‐ 8x10^9 CFU) or placebo mixed with breast milk for 28 days. Infant faecal samples and mother's breast milk will be collected at regular intervals during the study until 6 months of age. Additional infant stool samples will be collected at 12,18 and 24 months. Randomisation will be carried out online via the MedSciNet web portal (www.medscinet.com) and linked to the participant’s initial Subject ID. Allocation will be stored remotely from the main study database, so that members of the study team remain blinded to probiotic/placebo allocation. Recruitment and trial coordinators will not have access to the randomisation sequence. Subjects will be randomized at a 1:1 ratio of intervention to placebo. Minimisation will be based on parity and maternal pre‐pregnancy BMI >30. CONDITION: Infant gut microbiome ; Digestive System PRIMARY OUTCOME: 1.The change in infant faecal microbiota before, during and after probiotic or placebo supplementation by shotgun sequencing or next generation sequencing (NGS, e.g. Illumina MISeq or HiSeq) SECONDARY OUTCOME: 1.Biochemistry of infant stools by assessing pH levels, HMO and short‐chain fatty acids using liquid chromatography‐mass spectrometry may be performed on samples collected at Baseline (Day 4‐7), 1 month, 3 months, 6 months, 12 months, 18 months and 24 months.; 2. Comparison of the composition of the maternal and infant microbiome at baseline using shotgun sequencing or next generation sequencing.; 3.Adverse events will be recorded on daily and weekly adverse event logs, as well as infant health surveys, for the duration of the study. Medical records will be reviewed as needed for confirmation. INCLUSION CRITERIA: 1. Singleton pregnancies (primip or multi) 2. Pregnant women age 18 and above 3. Elective Caesarean section =37 weeks gestation 4. Maternal pre‐pregnancy BMI < 35kg/m² 5. Resident in UK for 3 years or more 6. Intention to exclusively breastfeed for at least 35 days, preferably for 6 months 7. Non‐smoker (gave up prior to pregnancy)