When a Spinal Tap May Be Necessary for Infant Fever

When your young baby has a fever, it's important to call your pediatrician. They might tell you what treatment to give your baby or ask you to bring your baby into the emergency room right away. This depends on how long your baby has had a fever, how high the fever is, and whether your child has other signs or symptoms of a serious illness. If there is any concern that your child could have meningitis (an infection of the fluid surrounding the brain and spinal cord), they may need to have a procedure called a spinal tap to aid with the diagnosis.

Mother checking temperature of young son
Jamie Grill / The Image Bank / Getty Images 

The Septic Work-Up

Unlike older children, it can be difficult to tell when a newborn or young infant is seriously ill. In fact, an infant under two or three months of age may have a serious bacterial infection, such as meningitis, bacteremia (a blood infection), or a urinary tract infection and still appear totally fine. That is why doctors routinely do a septic workup on infants who are under two or three months old when they have a rectal temperature that is at or above 100.4 degrees Fahrenheit.

This septic workup typically includes a:

  • Complete blood count
  • Blood culture
  • Urinalysis and urine culture
  • Spinal tap, which provides a sample of spinal fluid for analysis of cells and spinal fluid culture
  • Chest X-ray if there are signs of lung involvement
  • Stool studies if the baby has diarrhea
  • Viral test or culture, such as an RSV prep or flu test

Depending on these test results, a young infant with a fever may be started on antibiotics and might need to be hospitalized and observed for 24 to 48 hours. Sometimes infants can be sent home and scheduled for a follow-up visit to the pediatrician.

What Causes Babies to Have a Fever?

Just like older children, a baby's fever can be caused by a viral infection. Bacterial infections, which can be more serious than simple viral infections, are more common in younger children than in older children and young adults.

Does Your Baby Really Need a Spinal Tap for a Fever?

A spinal tap is an invasive test, but it is well-tolerated, and rarely has any complications. It is used to diagnose inflammation or infections of the nervous system, including meningitis and encephalitis (infection or inflammation of the brain tissue).

While you might be frightened about the idea of your child having an invasive diagnostic procedure, it is the standard of care because untreated infections in or near the brain can cause serious long-term consequences, including cognitive problems, epilepsy, hearing loss, and vision impairment. There are many types of meningitis, including those caused by viruses, bacteria, and fungi, and they are each treated differently based on the results of the spinal tap.

Of course, it is impossible to know in advance whether a spinal tap will show evidence of meningitis or encephalitis, and you might feel angry that your child had what you consider an unnecessary test if it turns out negative (no signs of infection). However, the potential adverse effect of untreated brain infection is far worse than the risk of a spinal tap.

What would your child's doctors do if you refused a spinal tap after a long discussion of the risks and benefits? It would likely depend on the situation, but it might range from observing the infant in the hospital to calling child protection services and charging the parent with medical neglect if they conclude that your refusal is putting your child's health in jeopardy.

Avoiding Viruses and Fevers

To help avoid fevers and the need for a septic workup, it can help to limit your baby's exposure to people during the first two or three months of her life. In particular, every person who holds your baby should wash their hands thoroughly. Those people who are unwell—even with a cold—should not touch or come too close to your baby. That may sound silly to new parents who want to show off their new baby, but the consequences may be exposing your baby to viruses and other germs, a fever, and a trip to the ER for a spinal tap.

Frequently Asked Questions

  • What is a spinal tap?

    A spinal tap is also known as a lumbar puncture. The procedure involves inserting a needle between two vertebrae to remove a sample of cerebrospinal fluid. 

    A spinal tap is used to diagnose nervous system infections such as meningitis and encephalitis. 

  • Why would a newborn need a spinal tap?

    If a newborn has a fever of unknown origin, the doctors may order a spinal tap or lumbar puncture. A lumbar puncture is used to diagnose meningitis, encephalitis, and other conditions that affect the nervous system. 

  • What is considered a high fever in an infant?

    A rectal temperature of 100.4 degrees F or higher is considered a high fever in babies. In children under 2 months of age, a fever of 100.4 degrees F is a medical emergency and should immediately be seen by a doctor.

    Between 2 and 3 months old, call the doctor if your baby has a rectal temperature of 100.4 degrees F or above. In children ages 3 months to 3 years, call the doctor for a fever of 102.2 degrees F or above.

    If the child is 2 months old or younger and has a fever of 100.4 degrees F,

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Detecting bacterial infections in newborns.

By Vincent Iannelli, MD
 Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.