Infectious Diseases During Pregnancy: What Are the Risks to Baby?

Infections during pregnancy can be spread to unborn babies

Doctor writing prescription for pregnant woman

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The excitement of a new life inside of a growing belly gives expectant parents a natural instinct to protect and provide for their baby. Pregnant people undergo emotions ranging from elation to paranoia about their babies’ well-being. In some cases, maternal hormones can be responsible for these mood swings.

But it is also important to remember that pregnancies are accompanied by weakened immune systems that can heighten the risk for infectious diseases. Certain infectious diseases pose a threat to a pregnancy and to a baby after they are born. This can include some common infections, like CMV, and some infections that are in the news, like Zika. CMV, in particular, is incredibly common.

What Are High-Risk Infections During Pregnancy?

A growing fetus can be thought of as a foreign object that the body accepts by lowering its immunity against it. A normal, active immune system recognizes foreign objects and mounts immune attacks against them. When that foreign object is a fetus, a self-programmed weakening of the immune system, or “immunosuppression,” is necessary for a successful pregnancy.

The danger, however, is that the immunosuppressive effect leaves both the gestating parent and developing fetus susceptible to several infectious diseases and complications. There also can be delays in diagnosing some infections during pregnancy, due to some diagnostic criteria that are naturally present in pregnancy.

For example, white blood cell counts are elevated in pregnancy. In addition, some discomfort and fatigue may be thought to be due to pregnancy rather than an infection.

What Are the Risks for the Baby?

"Vertical transmission” is a term that refers to the spread of infections from gestating parent-to-baby. These infections may occur while the fetus is still in the uterus (“in utero”), during and just following delivery, or after delivery.

Congenital infections

A congenital infection is an infection that crosses the placenta to infect the fetus. Many infectious microbes can cause congenital infections, leading to problems in fetal development, like microcephaly or other effects on brain development, or even death.

TORCH is an acronym for several of the more common congenital infections. TORCH infections include:

More recently we have learned also of the effects Zika can cause if the infection occurs during pregnancy.

Perinatal infections (during labor and delivery)

Perinatal infections refer to infections that occur as the baby moves through an infected birth canal. These infections can include but are not limited to, sexually-transmitted diseases. Infections can also occur through contamination with fecal matter during delivery.

Examples of perinatal infections are:

There are other infections as well. There may be more that we learn about.

With the help of health professionals, the transmission of these infections can be largely avoided (or the risks reduced).

In some cases, treatment may be available; in other cases, it may be necessary to change how the baby is delivered. It's important to talk to a doctor or other healthcare professional about any worrisome symptoms or known infections.

​Postnatal infections (after delivery)

Infections spread from parent to baby following delivery are known as “postnatal infections.” These infections can be spread during breastfeeding through infectious microbes found in a person's breastmilk. 

Some examples of postnatal infections are:

  • CMV
  • HIV
  • Hepatitis B and C
  • West Nile virus
  • Human T-cell lymphotropic virus (HTLV)

For both perinatal and postnatal infections, there is the risk that the infections may also be drug-resistant. This could especially be the case if an infection was acquired in the hospital, as hospital acquired infections are more resistant to antibiotic treatment. However, there are many other reasons for drug resistance.

What Tests Are Available?

Based on your medical history, risk factors, and exposure to certain infectious diseases, as well as results from ultrasounds and prenatal visits, your doctor will determine whether or not you need to undergo laboratory screening for certain congenital infections.

While several diagnostic tests are available for congenital infections, most obstetricians selectively test their patients based on their evaluation, rather than through routine screening.

During an ultrasound, a technician will be able to detect abnormalities that may be indicative of a congenital infection. They will look for abnormalities in development, such as the size of the baby, head size, as well as defects or underdevelopment of the heart, limbs, lungs, or abdomen.

After birth, a newborn who is suspected to have a congenital infection will be evaluated by examination of their physical development and through laboratory testing of blood samples. If anomalies are detected, the newborn will likely be tested for the presence of a specific infectious microbe.

If you are pregnant and are concerned about congenital infections, ask your healthcare provider about whether or not you should be tested for infections.

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8 Sources
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  1. Sappenfield E, Jamieson D, Kourtis A. Pregnancy and susceptibility to infectious diseases. Infect Dis Obstet Gynecol. 2013;2013:1-8. doi:10.1155/2013/752852

  2. National Institute of Child Health and Human Development (NICHD). What infections can affect pregnancy?. Updated April 27, 2021.

  3. Chandra S, Tripathi A, Mishra S, Amzarul M, Vaish A. Physiological changes in hematological parameters during pregnancy. Indian Journal of Hematology and Blood Transfusion. 2012;28(3):144-146. doi:10.1007/s12288-012-0175-6

  4. Arora N, Sadovsky Y, Dermody T, Coyne C. Microbial vertical transmission during human pregnancy. Cell Host Microbe. 2017;21(5):561-567. doi:10.1016/j.chom.2017.04.007

  5. Gérardin P, Sampériz S, Ramful D et al. Neurocognitive outcome of children exposed to perinatal mother-to-child chikungunya virus infection: The CHIMERE cohort study on Reunion Island. PLoS Negl Trop Dis. 2014;8(7):e2996. doi:10.1371/journal.pntd.0002996

  6. Lawrence R. Transmission of infectious diseases through breast milk and breastfeeding. Breastfeeding. 2011:406-473. doi:10.1016/b978-1-4377-0788-5.10013-6

  7. Centers for Disease Control and Prevention (CDC). CDC Winnable Battles Progress Report. Updated December 14, 2017. 

  8. Emory School of Medicine. Congenital infections