close Cancel email WhatsApp link share Share bookmark SaveA potential new cause of male infertility has been found – harmful bacteria in semen. When men have certain kinds of bacteria in their semen, their partner is less likely to get pregnant, early-stage Danish research has found. The study involved couples who were either having fertility treatment or who had repeated miscarriages – but the bacteria may lower fertility for all couples, said the researchers. But the three types of bacteria implicated in the latest research – Gardnerella, Fannyhessea and Prevotella – are not classed as STDs. Most beneficial vaginal bacteria are a type called Lactobacillus, which create acidic conditions that stop the growth of harmful bacteria and fungi.