Certain infectious agents have been identified more frequently in cultures from women who have had spontaneous pregnancy losses. These include Ureaplasma urealyticum, Mycoplasma hominis, and Chlamydia. A recent observational study reported an increased frequency of chronic endometritis in women with multiple miscarriages and improved outcomes after treatment with antibiotics.

Strong evidence suggests an important role of Mycoplasma and Ureaplasma as a potential cause of RPL. In most cases there are no signs or symptoms of an infection such as a discharge, rash, odor, or irritation. These infections of the uterus are often called ‘silent infections’ because they are not detected unless sensitive and specific tests are preformed. Mycoplasma and Ureaplasma positive cultures are strongly associated with preterm delivery. Diagnosis and treatment of Mycoplasma following a first or later pregnancy loss significantly reduces pregnancy loss in the next pregnancy. Mycoplasma and Ureaplasma infections have been a proven cause of bovine abortion for over 35 years. Our own data from The Recurrent Pregnancy Loss Center published in 2016 includes over 1,850 women with RPL, clearly demonstrates that women with RPL have a two-fold increase risk of Mycoplasma and Ureaplasma than control women of the same age, race and body mass index.

Other less frequent pathogens include toxoplasma gondi, rubella, HSV, measles, CMV, coxsackievirus and listeria monocytogenes.  It is important to be aware that none of these pathogens have been causally linked to RPL. Because of the association with sporadic pregnancy losses and the ease of diagnosis, we recommend testing women with RPL and treatment for the appropriate pathogen.