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Overview of Infections in Newborns


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Jul 2020| Content last modified Jul 2020
Click here for the Professional Version

Infections occur at all ages but are a great cause for concern in newborns because newborns, especially premature ones, have an underdeveloped immune system and are more susceptible to infection. Although certain protective antibodies pass from the mother to the fetus through the placenta (the organ that provides nourishment to the fetus), the levels of antibodies in the fetus's blood may not be high enough to fight an infection.

Fetuses and newborns can acquire an infection in the following ways:

  • In the womb

  • During birth

  • After birth

Infection acquired in the womb (in utero infection)

An infection in the fetus, which can occur any time before birth, results from an infection in the mother. Sometimes doctors and the mother know she has an infection, but sometimes they do not. The mother's infection is passed to the fetus through the placenta.

Common infections that are passed on via the placenta include rubella, toxoplasmosis, cytomegalovirus, Zika virus infection, and syphilis. Human immunodeficiency virus (HIV) infection and hepatitis B virus infection may also sometimes be passed on via the placenta. There are also many rarer infections that can infect the fetus before birth.

Problems for the fetus depend on which organism is causing the infection and when the mother's infection occurred during the pregnancy. Problems include miscarriage, slow growth in the uterus, premature birth, stillbirth, and birth defects. An infection may or may not cause symptoms in the mother.

Infection acquired during birth (intrapartum infection)

An infection can be acquired during birth if the baby passes through an infected birth canal or if an infection moves up from the vagina if delivery is delayed after the membranes have ruptured.

Infections that can occur during birth include HIV infection, herpes simplex virus infections, hepatitis B virus infection, streptococcal infections, E. coli infections, listeriosis, gonococcal infections, and chlamydia. Sometimes these infections can also be passed on through the placenta.

Infection acquired after birth (postpartum infection)

An infection acquired after birth occurs when a newborn has close contact with an infected mother directly or through breastfeeding. An infection acquired after birth can also occur if newborns have contact with infected health care practitioners, family, or visitors in the hospital (see Hospital-Acquired Infections in Newborns) or at home.

Types of infections in newborns

Infections in newborns are usually caused by bacteria or viruses and less commonly by fungi or parasites. Bacteria include group B streptococci, Escherichia coli (E. coli), Listeria monocytogenes, gonococci, and chlamydiae. Viruses include herpes simplex viruses (HSV), human immunodeficiency virus (HIV), cytomegalovirus (CMV), and hepatitis B virus (HBV).

Some infections that can affect people of all ages cause particular problems when they occur in a fetus or newborn. Some of the more serious infections in newborns include the following:

See Candidiasis (Yeast Infection) for infection caused by the fungus Candida.

Diagnosis of Infections in Newborns

  • A doctor's examination

  • Various tests

Doctors suspect an infection based on the newborn's symptoms or abnormalities (such as birth defects) and on the results of a physical examination.

Doctors also do blood tests and test samples of the newborn's blood, spinal fluid, urine, saliva, or tissues to determine which organism is causing the infection. The mother may also be tested.

Treatment of Infections in Newborns

  • Antibiotics or antiviral drugs

These infections are treated based on which organism is causing the infection.

Some bacterial infections can be treated with antibiotics.

Some viral infections may be treated with antiviral drugs.

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Test your knowledge

Occult Bacteremia
Occult (hidden) bacteremia is the presence of bacteria in the bloodstream. A child with occult bacteremia may have a fever but otherwise look well, with no obvious source of infection. To which of the following age groups of children is this condition almost exclusively limited?
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