Why does my baby’s urine smell?

Editor’s Note: Dr. Jennifer Shu, CNNHealth’s Living Well expert doctor, is a practicing pediatrician and mother of two.

Q: My baby’s urine smells really bad! Is there something wrong?

A new study published in this week’s journal Pediatrics suggests that a combination of fever and foul-smelling urine can be a sign of a urinary tract infection in babies.

Researchers surveyed the parents of more than 300 children between 1 and 36 months of age with a fever. Of those children, 57% who reported to smelly urine were discovered to have a urinary tract infection. Only 32% of those without smelly urine had a UTI.

The smell is thought to come from intestinal bacteria that have entered the urinary tract and multiplied to the point of causing an infection.

Fever in a young child without an explained cause, such as a cold or ear infection, might be written off with the assumption that it is being caused by a virus. Left untreated, UTIs can lead to increased fevers and possible kidney problems.

If your child has a fever, you may want to sniff and see if his or her diaper smells out of the ordinary. If so, be sure to bring the stinky urine to your pediatrician’s attention so tests can be performed to check for a UTI.

Of course, that’s not the only explanation for smelly urine. As a parent changing your baby’s wet diaper, you may notice a light smell of ammonia and other normal waste from the kidneys.

Urine may also have a stronger odor when it is more concentrated, such as first thing in the morning, or during times of illness and mild dehydration.

It is well known that certain foods can cause a change in the urine’s smell (asparagus comes to mind), and medications such as penicillin also create a characteristic odor.

Plus, rare metabolic disorders and diabetes can give a sweet smell to one’s urine.

Bottom line? Check with your doctor if you notice the smell persists.