Study Links Semen Microbiome Imbalance to Miscarriage and Lower IVF Success

Research published in The Lancet shows that disruptions in the bacterial community of semen are associated with increased miscarriage risk and fewer live births after assisted reproduction.

A recent article in The Lancet Obstetrics, Gynaecology & Women’s Health reports that the composition of bacteria, viruses and fungi in seminal fluid may influence reproductive outcomes. Analyzing over 350 women and nearly 200 men from two Danish university hospitals, the team found that men whose semen displayed a bacterial profile resembling bacterial vaginosis experienced lower live-birth rates—57% versus 85% when the profile was absent—and a higher incidence of miscarriage.

The study also linked a disturbed female gut microbiome to reduced pregnancy success, while the vaginal microbiome showed no clear association with live births. Researchers describe the seminal imbalance as “dysbiosis” but note that the mechanisms remain uncertain and causality has not been established. They warn against premature use of antibiotics or dietary interventions, emphasizing the need for larger, more diverse studies to confirm the findings.