Background: Past decades have witnessed a decrease in environmental biodiversity. We hypothesized a similar decrease in indigenous gut microbiota diversity, which may have contributed to the obesity epidemic.
Objective: To investigate the changes in the composition and function of the gut microbiota in pregnant women over a period of 20 years.
Study design: Altogether 124 pregnant women (41 overweight and matched 83 normal weight) pregnant in 1997, 2007 or 2017 were included in the study. The gut microbiota composition was assessed from fecal samples obtained at 32 weeks of gestation by 16S rRNA gene sequencing. Fecal short chain fatty acid (SCFA) profiles were measured by gas chromatography mass spectrometry (GC-MS).
Results: Distinct gut microbiota profiles were detected in pregnant women from 1997, 2007 and 2017 (PERMANOVA Bray-Curtis R2 = 0.029, p = 0.001). The women pregnant in 1997 exhibited significantly higher microbiota richness and diversity as compared to those pregnant in 2007 and 2017. The total concentration of fecal SCFAs was significantly higher in the pregnant women in 1997 compared to those in 2007 and 2017. Significant differences in gut microbiota composition between normal weight and overweight women were manifest in 1997 but not in 2007 or 2017.
Conclusions: The decrease in intestinal microbiota richness and diversity over two decades occurred in parallel with the decline in biodiversity in our natural surroundings. It appears that the gut microbiota of pregnant women has changed over time to a composition typical for overweight individuals.
Keywords: Fecal short-chain fatty acids; gut microbiota; obesity; overweight; pregnancy.
The composition of the indigenous gut microbiota was investigated in pregnant women from three different time periods (1997, 2007 and 2017) in the same geographical and cultural area in Southwest Finland. Distinct gut microbiota profiles were evident in the women from the different time periods. The women pregnant in 1997 exhibited significantly higher microbiota richness and diversity as compared to the pregnant women from 2007 to 2017. The cause of the loss of gut microbiota richness and diversity over time remains obscure, since no major changes in the population, dietary practices or antibiotic use occurred in the area during the course of the study periods. Gut microbiota composition has been suggested to play a causal role in the development of overweight and obesity. In line with this notion, significant differences in the gut microbiota composition between normal weight and overweight were detectable in women pregnant in 1997. However, no such differences were manifest in women pregnant in 2007 or 2017 and the gut microbiota of these individuals resembled that of overweight pregnant women from 1997. The results of the study provide direct evidence for a decline in gut microbiota diversity over time in the same geographical area and the same population. It furthermore appears that the gut microbiota of pregnant women has changed over time to a composition typical for overweight individuals. The gut microbiota profiles may thus provide insight into the development and intergenerational transfer of overweight.