Am J Clin Nutr

Background: Despite the importance of gestation period for human health, studies addressing the impact of maternal microbiota on its progression and its modulation by maternal lifestyle are scarce. Although most of the evidence in the field comes from observational studies, we recently described how some lifestyle interventions during pregnancy reduced the small-for-gestational-age (SGA) incidence. We hypothesized the pregnant individual's microbiome modulation as potential mechanism by which lifestyle interventions could impact gestation progression.

Objectives: The objectives of this study was to investigate the effect of pregnancy lifestyle interventions, based on a Mediterranean dietary pattern (MD) or Stress Reduction program (SR) that proved to be beneficial in reducing the SGA incidence, on the pregnant individuals' gut and vaginal microbiota as exploratory outcomes.

Methods: In a random subsample (n = 351) from a trial including pregnancies randomly allocated into an MD intervention, an SR program, or non-intervention, maternal fecal/vaginal samples were collected at the end of the interventions, and in a subset (n = 85) also at recruitment. Microbiota was profiled by 16S rRNA gene sequencing. Multivariate models evaluated the associations of microbiota with the interventions.

Results: Mothers included in the study presented a similar gut microbiota profile before the intervention; pregnancy MD intervention influenced the overall structure of gut microbiota, (R2 = 0.008, F = 1.885, P = 0.002), which resulted in enrichment in Firmicutes phylum (Coeff = 0.06, 95% confidence interval [CI]: 0.002, 0.118), related to the increment in health-associated taxa (Lachnospiraceae/Ruminococcaceae families) and other SCFA producers; and diminishment in Campylobacter genus (Coeff = -0.91, 95% CI: -1.361, -0.459). The link of the SR program with gut microbiota was more limited; however, some key components from these families were also affected. Microbial diversity of gut microbiota decreased as pregnancy progressed, with this effect more observable in the mothers that followed the interventions. The interventions have a negligible association with the vaginal microbiota.

Conclusions: Pregnancy lifestyle interventions influence maternal gut microbiota. The trial was registered at clinicaltrials.gov Identifier as NCT03166332.

Clinical trial information: Date of Institutional Review Board approval and registration: 16 December 2016; 19 April 2017; Date of initial participant enrollment and date of first outcome (i.e., delivery of the pregnant individual enrolled): 1 February 2017; 10 May 2017.