Evidence check: FUT2 in the context of fertility

FUT2 encodes a fucosyltransferase that determines secretor status (whether ABO antigens are secreted into body fluids). Some studies suggest that non-secretor status (due to FUT2 variants) may be associated with recurrent pregnancy loss or reduced fertility, possibly via altered vaginal microbiome or immune modulation. However, the evidence is inconsistent: some meta-analyses show moderate associations, others find none. Effect sizes are small, and mechanisms remain incompletely understood. Consumer DNA tests like MyBody-X often label such variants as 'genetic risk' without clinical context. Genotyping alone is insufficient for fertility diagnosis or treatment decisions. For fertility issues, comprehensive clinical workup (hormones, semen analysis, gynecological exam) is essential. FUT2 genetics may serve as a supplementary clue, not a basis for action. Caveat: the literature is conflicting, with many studies underpowered or lacking replication. Therefore, the evidence is rated as 'unclear'.