Association between gut microbiota and spontaneous abortion: A two-sample Mendelian randomization study

Recent studies have reported an association between gut microbiota composition and spontaneous abortion (SA). However, the causal effect of gut flora on spontaneous abortion is unclear.

A two-sample Mendelian study utilized summary statistics of the gut microbiota from the most extensive meta-analysis of genome-wide association studies conducted by the MiBioGen consortium. Pooled statistics for spontaneous abortion were derived from data published by a UK Biobank study. Inverse variance weighting, Mendelian randomization (MR)-Egger and weighted modeling methods were used to test the causal relationship between gut microbiota and spontaneous abortion. Reverse Mendelian randomization analysis was performed on bacteria found to be causally associated with spontaneous abortion. The level of heterogeneity of the instrumental variables was quantified using Cochran's Q statistic.

Inverse variance weighting identified flora causally associated with spontaneous abortion: Paraprevotella genus (odds ratio [OR] 1.001, 95% confidence interval [CI] 1.000-1.002, P = 0.005), Clostridium genus (OR 1.001, 95% CI 1.000-1.003, P = 0.006), Bacillus-like S24-7 group (OR 1.002, 95% CI 1.000-1.003, P = 0.009), Flavonifractor genus (OR 0.998, 95% CI 0.996-0.999, P = 0.010), genus Lachnospiraceae UCG001 (OR 1.002, 95% CI 1.000-1.003, P = 0.019), and the Christensenella spp. R7 group (OR 1.002, 95% CI 1.000-1.003, P = 0.025). No significant causal effect of spontaneous abortion on the gut microbiota was found based on the results of the reverse MR analysis.

This study provides genetic evidence supporting the existence of a causal relationship between the gut microbiota and spontaneous abortion. However, further exploration of the specific biological roles played by genetic variations is still needed.