Infection of the reproductive tract has been linked to pregnancy loss, but strong evidence in support of infection being a cause of recurrent loss is speculative at best. The most extensively studied organisms are mycoplasma, ureaplasma, Chlamydia, and Group B streptococcus. Bacterial vaginosis has also been associated with losses after 12 weeks of gestation. The association with these organisms and recurrent loss is unlikely given the results of a large prospective study involving 70 patients with recurrent loss which found no correlation with present or past infection with any of these bacteria.
Certain viruses have also been associated with loss including herpes simplex virus (HSV) and human cytomegalovirus (CMV) which may directly infect the placenta. These viruses may be involved in intrauterine growth restriction, premature rupture of membranes, and preterm birth, but their role in recurrent miscarriage remains speculative.
An inflammatory condition known as endometritis which is inflammation of the endometrium or uterine lining has also been associated with both infertility and recurrent pregnancy loss. Endometritis can be caused by a recent or past infection or may rarely occur after pregnancy loss or even instrumentation (following a D&C or D&E).
Whether chronic infection is a cause of recurrent pregnancy loss is not precisely known. An individual’s susceptibility to an infectious organism may be the determining factor in whether pregnancy loss occurs. Other probable factors include primary exposure to an infection during early pregnancy, capability of the infection to cause uterine and placental infection, development of an infectious state, and immunocompromise of the person infected. It is known that infection causing fevers over 102 degrees Fahrenheit can potentially kill embryos and destroy early pregnancies. Therefore measures to decrease the likelihood of a high fever (acetaminophen) even in illnesses like influenza are important in those attempting pregnancy and during early pregnancy.