Some viral and bacterial infections increase the risk of pregnancy loss. While a few infectious illnesses are well documented risk factors for miscarriage, some newer studies indicate that even a few common vaginal infections can mean an increased risk of miscarriage.
Some of these infections are limited in course but others can be chronic. Remember that if you are concerned that you may have any of these infections that you should talk to your doctor about testing and/or treatment.
Bacterial vaginosis is a common vaginal infection that causes a fish-like odor, itching, burning after intercourse, and thin white or gray vaginal discharge. Some women may have no symptoms at all. Some research has tied bacterial vaginosis infection in pregnancy to both first and second trimester miscarriage, as well as higher risk of preterm delivery, although researchers are still examining how this specific infection relates to miscarriage.
Doctors have long known that chlamydia and other sexually transmitted diseases boost the odds of developing pelvic inflammatory disease, a risk factor for ectopic pregnancy. Researchers have found evidence that chlamydia might increase miscarriage risk in another way also -- a 2007 study found evidence the bacteria can alter immune response against an early pregnancy.
Certain types of bacterial food poisoning, such as Listeria and Salmonella infections, are tied to miscarriage risks. Listeria is a risk in unpasteurized cheese and deli meats, which causes the disease listeriosis, and Salmonella is common in poultry, red meat, and uncooked eggs.
If you have ever heard the recommendation that pregnant women should not change litter boxes, the reason is that some cats carry a bacteria called Toxoplasma gondii. These bacteria cause a disease called toxoplasmosis, which can cause miscarriage or congenital problems in a baby.
Parvovirus B19 causes a relatively mild illness called fifth disease. The condition is usually mild in children, and the majority of adults are immune (because most people catch the disease at some point during childhood, which leads to permanent immunity). Parvovirus B19 can cause hydrops fetalis if a non-immune pregnant woman is exposed, but the CDC states that less than 5% of women who get parvovirus B19 during pregnancy end up miscarrying.
Rubella, also called German measles, can cause congenital birth defects if a pregnant woman catches it in her first trimester, and it can also cause miscarriage. Rubella is not common, however, due to widespread vaccination against the virus that causes it (the R component of the MMR vaccine). Doctors routinely test women for immunity against rubella as part of prenatal blood testing.
Azenabor, Anthony A., Patrick Kennedy, and Salvatore Balistereri, "Chlamydia trachomatis Infection of Human Trophoblast Alters Estrogen and Progesterone Biosynthesis: an insight into role of infection in pregnancy sequelae." International Journal of Medical Sciences 2007. Accessed 5 Jan 2008. Centers for Disease Control and Prevention, "Parvovirus B19 Infection and Pregnancy." 21 Jan 2005. Accessed 6 Jan 2008. Leitich, Harald, Barbara Bodner-Adler, Mathias Brunbauer, Alexandra Kaider, Christian Egarter, and Peter Husslein. "Bacterial vaginosis as a risk factor for preterm delivery: A meta-analysis." American Journal of Obstetrics and Gynecology 2003. Accessed 4 Jan 2008.
Centers for Disease Control and Prevention, "Parvovirus B19 Infection and Pregnancy." 21 Jan 2005. Accessed 6 Jan 2008.
Leitich, Harald, Barbara Bodner-Adler, Mathias Brunbauer, Alexandra Kaider, Christian Egarter, and Peter Husslein. "Bacterial vaginosis as a risk factor for preterm delivery: A meta-analysis." American Journal of Obstetrics and Gynecology 2003. Accessed 4 Jan 2008.