Both bacterial and viral infectious sources for recurrent pregnancy loss have been proposed. In particular, the presence of either of two types of bacteria—ureaplasma or mycoplasma—within the cervix or uterus has been suggested as a risk factor for pregnancy loss. The scientific evidence is somewhat lacking to prove this connection, but we routinely culture our patients for ureaplasma and mycoplasma and treat both members of a sexually intimate couple when and if these bacteria are found.Women who become infected with Listeria (a type of bacterial food poisoning) after eating unpasteurized dairy products can also miscarry as a result of a uterine infection from these bacteria.

Similarly, certain viral infections can cause miscarriage if contracted during pregnancy. Parvovirus B19 causes a mild viral illness in children known as fifth’s disease. Children who contract this illness have a fever and bright red cheeks, lending the disease its other common name of “slapped cheek syndrome.” Unfortunately, women who contract this illness during pregnancy can suffer miscarriage even in the second and third trimesters. Once infected, an individual becomes immune to this virus, so parvovirus B19 would not cause repetitive pregnancy loss. No vaccine exists for parvovirus B19.