Ability of Bifidobacterium breve 702258 to transfer from mother to infant: the MicrobeMom randomized controlled trial

The composition of the infant microbiome can have a variety of short- and long-term implications for health. It is unclear if maternal probiotic supplementation in pregnancy can affect the infant gut microbiome.

This study aimed to investigate if maternal supplementation of a formulation of Bifidobacterium breve 702258 from early pregnancy until 3 months postpartum could transfer to the infant gut.

This was a double-blinded, placebo-controlled, randomized controlled trial of B breve 702258 (minimum 1 × 10⁹ colony-forming units) or placebo taken orally from 16 weeks' gestation until 3 months postpartum in healthy pregnant women. The primary outcome was presence of the supplemented strain in infant stool up to 3 months of life, detected by at least 2 of 3 methods: strain-specific polymerase chain reaction, shotgun metagenomic sequencing, or genome sequencing of cultured B breve. A total of 120 individual infants' stool samples were required for 80% power to detect a difference in strain transfer between groups. Rates of detection were compared using the Fisher exact test.

A total of 160 pregnant women with average age of 33.6 (3.9) years and mean body mass index of 24.3 (22.5-26.5) kg/m², of whom 43% were nulliparous (n=58), were recruited from September 2016 to July 2019. Neonatal stool samples were obtained from 135 infants (65 in intervention and 70 in control group). The presence of the supplemented strain was detected through at least 2 methods (polymerase chain reaction and culture) in 2 infants in the intervention group (n=2/65; 3.1%) and none in the control group (n=0; 0%; P=.230).

Direct mother-to-infant strain transfer of B breve 702258 occurred, albeit infrequently. This study highlights the potential for maternal supplementation to introduce microbial strains into the infant microbiome.