Infections During Pregnancy

ByJessian L. Muñoz, MD, PhD, MPH, Baylor College of Medicine
Reviewed/Revised Sept 2024
VIEW PROFESSIONAL VERSION

Most common infections that occur during pregnancy, such as those of the urinary tract or respiratory tract, cause no serious problems. However, some infections can be passed to the fetus before or during birth and harm the fetus (such as, causing deafness) or cause a miscarriage, stillbirth, or preterm birth.

Sexually transmitted infections that can cause problems include the following:

  • Chlamydia may cause prelabor rupture of the membranes or preterm labor. It can also cause eye infection (conjunctivitis) in newborns.

  • Gonorrhea can also cause conjunctivitis in newborns.

  • Syphilis can be transmitted from a mother to the fetus through the placenta. Syphilis in the fetus can cause several birth defects, stillbirth, or problems in the newborn. Pregnant women are routinely tested for syphilis early in the pregnancy. Usually, treatment of syphilis during pregnancy cures both mother and fetus.

  • Human immunodeficiency virus (HIV) infection is transmitted to the fetus in about one-fourth of pregnancies if women who have the infection are not treated. Women with HIV infection should take antiretroviral medications—this is particularly important during pregnancy. For some women with HIV infection, cesarean delivery, planned in advance, may further reduce the risk of transmitting HIV to the baby.

  • Genital herpes can be transmitted to the baby during a vaginal delivery. Babies who are infected with herpes can develop a life-threatening brain infection called herpes encephalitis. A herpes infection in babies can also damage other internal organs and cause seizures, skin and mouth sores, permanent brain damage, or even death. If women have a previous history of genital herpes, they should take medications in late pregnancy to prevent active herpes at the time of delivery. In late pregnancy, if women have symptoms of herpes or develop herpes sores in the genital area late in pregnancy, the vulvovaginal area should be tested for herpes. If an active infection is confirmed, women are usually advised to give birth by cesarean delivery.

  • Zika virus infection in a pregnant woman can cause the baby to have a small head (microcephaly). The head is small because it does not develop normally. Zika virus infection can also cause eye abnormalities in the baby. The Zika virus is spread by mosquitoes, but it can also be spread through sexual intercourse, through blood transfusions, and from a pregnant woman to her baby before or during birth.

Other infections that can cause problems include the following:

Hepatitis may be transmitted sexually but is often transmitted in other ways. Thus, it is not typically considered a sexually transmitted infection. Hepatitis in a pregnant woman can increase the risk of preterm birth. It can also be transmitted from the mother to the baby during delivery, causing problems.

Treatment of Infections During Pregnancy

  • Sometimes medications, depending on the balance of benefits and risks

To determine whether to treat pregnant women with antibiotics (or antivirals), doctors weigh the risks of using the medication against the risks of the infection.

Some antibiotics

Other antibiotics, including tetracyclines and fluoroquinolones, may cause problems in the fetus (see table Some Medications and Risk of Problems During Pregnancy).

Most antiviral medications are safe in pregnancy, but pregnant women should talk with their doctor before starting any medications.

Doctors also consider whether treatment is likely to have any benefits. For example, if women have bacterial vaginosis but no symptoms and if the pregnancy is not considered high-risk, treating bacterial vaginosis is not known to have any benefits.

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