Viruses, bacteria, and other germs cause infections. You may be more likely to get an infection during pregnancy because your immune system is naturally suppressed. Many infections do not cause problems, but some can cause problems for you, your developing baby, or both. If you think you have an infection during pregnancy, it is important to talk to your doctor as soon as possible.

Significant infections during pregnancy include:


Varicella (chickenpox) is caused by a virus that commonly affects children. Over 90% of pregnant women are immune to chickenpox. If you are immune to chickenpox, it is unlikely that you will get it again. About one in 2,000 women will develop chickenpox during pregnancy. If you get chickenpox in the first 20 weeks of pregnancy, there is a very small chance (less than 1%) that your baby will be born with serious birth defects. If you get chickenpox around the time of delivery, your baby may be born with chickenpox infection. If this infection is treated, most babies have only a mild illness. Without treatment, up to 30% of infants die.


Chorioamnionitis is a rare but serious bacterial infection of the tissue surrounding the amniotic fluid and the baby. It usually starts when bacteria in your vagina or rectum enters your womb. It is more likely to occur after the bag of water has broken later in pregnancy. Chorioamnionitis happens in about 2% of term pregnancies, and 5% to 10% of preterm pregnancies in the United States. In most cases, having this infection means your baby must be delivered as soon as possible.


Cytomegalovirus (CMV) is a common viral infection that usually does not cause symptoms. By age 40, over half of all adults in the United States have been infected with CMV. About 1% to 4% of pregnant women become infected with CMV for the first time. When a pregnant woman becomes infected, she can pass the virus on to her developing baby. In a small number of cases, this leads to serious illness in the newborn, lasting disabilities, and even death.

Group B Streptococcus

Group B streptococcus (GBS) is a type of bacterium. Many people carry GBS, but do not become ill. About 25% of pregnant women carry GBS in the rectum or vagina. A developing baby may come in contact with this bacteria before or during birth if the mother carries GBS. It can cause life-threatening infections in newborns. In pregnant women, GBS can cause bladder infections, infections of the womb, and stillbirth. All pregnant women who test positive for GBS are treated with IV antibiotics during labor.


Listeriosis is a rare infection caused by bacteria found in some contaminated foods. About 1,700 people get listeriosis each year. Pregnant women are more likely to get listeriosis. Listeriosis can cause serious problems, such as premature delivery, miscarriage, and severe illness or death of your newborn.

Parvovirus B19 Infection

Parvovirus B19 infection (fifth disease) is a common virus that causes a "slapped-cheek" rash on the face. More than 50% of all adults have had this virus. This infection happens most often in children. If you have contact with a person who has fifth disease, there are usually no serious problems for you or your developing baby. Rarely, parvovirus B19 infection can cause a developing baby to have severe anemia (low iron), swelling, stillbirth, or miscarriage.


Rubella (German measles) is a mild childhood illness but it can cause serious birth defects in a developing fetus. For women who develop rubella in the first trimester of their pregnancy, there is a 20% chance that their baby will be born with one or more birth defects. These can include eye problems, hearing loss, heart defects, and intellectual disabilities. With the widespread use of the rubella vaccine, major outbreaks of rubella no longer happen in the United States. Still, small outbreaks do happen.

Sexually Transmitted Diseases

Some sexually transmitted diseases (STDs), such as genital herpes, gonorrhea, chlamydia, herpes simplex virus, and bacterial vaginosis, are commonly found in pregnant women. Other STDs, such as HIV and syphilis , are less commonly found in pregnant women. STDs can cause:

  • Infertility (not being able to get pregnant in the future)
  • Premature labor
  • Premature breaking of the membranes surrounding the developing baby
  • Infection of the uterus after delivery

Some STDs can be passed from you to your baby before, during, or after birth. Treatment throughout pregnancy and precautions during birth can help keep the baby safe.


Toxoplasmosis is caused by a parasite. The parasite lives in the intestine of cats and is shed in cat feces, mainly into litter boxes and garden soil. Toxoplasmosis can cause serious problems in a developing baby. Each year in the US, approximately 400-1,000 babies are born with this condition. Toxoplasmosis can cause blindness, hearing loss, learning disabilities, miscarriage, and stillbirth.

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