Semen microbiome imbalance linked to higher pregnancy loss, study finds

A study published in The Lancet Obstetrics, Gynaecology & Women's Health examined 353 women and 191 male partners from Denmark and Sweden. The researchers found that bacterial imbalance (dysbiosis) in male semen was associated with lower live‑birth rates and higher rates of pregnancy loss among couples undergoing IVF or with recurrent miscarriage. Among IVF couples, 57% of those with semen dysbiosis had a baby compared with 85% without the imbalance, and miscarriage risk was about 26 percentage points higher when the male partner had the imbalance.

In a separate investigation published in Cell Host & Microbe, scientists at the University of Beijing identified that the endometrial bacterium Lactobacillus gasseri declines with age. Experiments with human cells and mice showed that supplements containing this bacterium or its derivatives improved uterine conditions and embryo implantation in women over 35, suggesting a potential new treatment to boost fertility in older women.