Premature babies are typically more vulnerable to infections because their immune systems are immature. They cannot fight off bacteria, viruses or fungi in the same way that full-term babies may be able to.
The immune system
The immune system defends against infections caused by bacteria, viruses or fungi. At birth, a premature baby will not have a well-developed immune system, and exposure to new organisms will place the baby at risk for infection.
Usually, a pregnant person’s antibodies cross through the placenta during the third trimester of pregnancy. This gives the newborn some protection against diseases that they have not yet been exposed to in the outside environment. Because premature babies miss either some or even all of the third trimester, much less of the pregnant person’s immunity is transferred to the baby before birth.
Additionally, because the premature baby’s immune system is immature, it may have difficulty producing the cells and proteins that make up the components necessary to fight infection.
Infection
Premature babies are highly susceptible to infection for several reasons:
- Their immune systems are both immature and inexperienced. This means that every encounter with a germ that is new to the baby may cause an infection, and the baby’s immune system may be slow to develop the means to fight the infection.
- They miss the usual transfer of the birthing parent’s antibodies through the placenta to the fetus during the third trimester of pregnancy.
- The possibility for infection can be great for a premature baby in the Neonatal Intensive Care Unit (NICU). Preterm babies often need breathing support and intravenous (IV) lines for nutrition. These can serve as points of entry for organisms that can cause infection.
Infection in a premature baby may affect some or all parts of the body and can have varying degrees of severity.
A serious infection in a premature baby may be suspected if the baby shows any of the following signs:
- lethargy or decreased responsiveness
- irritability
- fever, low body temperature or fluctuations in body temperature
- abnormal breathing
- pale or blue skin
- apnea (pause in breathing) or bradycardia (slow heart rate)
Infections in premature babies may occur anywhere in the body, including the lungs, blood, urinary tract or cerebrospinal fluid (the fluid in the spine and surrounding the brain). In general, if an infection is suspected, blood and urine samples will be collected. In many cases, samples of the cerebrospinal fluid and of the secretions in the lungs may also be collected. These samples are tested to identify the organism causing the infection and the best antibiotic to use. Since treatment must start before the results are available, the initial choice of antibiotics must cover the most likely possible causes of the suspected infection. Once the results of the samples are available, the health-care team can select the specific antibiotic and how long to give the antibiotic treatment.
