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Infectious Diseases during Pregnancy - Risks to baby

Infections during pregnancy can be spread to unborn babies


Updated May 27, 2014

The excitement of a new life inside of a growing belly gives expectant mothers a natural maternal instinct to protect and provide for her baby. Pregnant women 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 several infectious diseases.

Why are pregnant women and unborn babies considered high-risk for some infectious diseases?

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 mother and developing fetus susceptible to several infectious diseases and complications that normally do not occur in healthy children.

What are the infectious disease risks for unborn babies?

”Vertical transmission” is a term that refers to the spread of infections from mother-to-baby. These infections may occur while the fetus is still in the uterus (“in utero”), during labor and delivery, or after delivery (such as while breastfeeding).

The following infections can be spread from mother-to-baby:

  1. Congenital infections (passed in utero)

  2. 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 or even death.

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

  • 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. For example, infections can also occur through contamination with fecal matter during delivery.

    Examples of perinatal infections are:

  • Postnatal infections (after delivery)

    Infections spread from mother to baby following delivery are known as “postnatal infections.” These infections can be spread during breastfeeding through infectious microbes found in the mother’s breastmilk.

    Some examples of postnatal infections are:

  • What kind of tests are available for congenital infections?

    Based on a patient’s 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 good technician will be able to detect abnormalities that may be indicative of a congenital infection. He 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 his physical development and through laboratory testing of blood samples for levels of liver proteins, antibodies, platelets, and blood cells. 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.


    Ford-Jones, EL and Ryan, G. Implications for the Fetus of Maternal Infections in Pregnancy. Infectious Diseases, 2nd Edition. Cohen J and Powderly WG, editors. Elsevier Limited. ©2004.

    Mims CA, Playfair JH, Roitt, IM, Wakelin D, Williams R, and Anderson RM. Obstetric and Perinatal Infections. Medical Microbiology. Mosby-Year Book Europe Limited. ©1993. pp. 26.1-26.8.

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