Parents have been asking me a whole lot of questions about the tiny hole they sometimes find over the lower back of their babies.

Let me see if I can make things simple about these things we call sacral dimples.

Dimples or pits at the base of the tailbone just above or in the buttock crease occur in at least 2-3% of newborns.

This tiny hole results during the closure of the lining around the spinal cord.

Usually, these holes connect to nothing and are no problem whatsoever, but they can also represent a problem in the closing off of the spinal cord from the skin. This can allow a channel to exist between the two which can predispose your child to an infection that tracks inward from the skin to the spinal cord. It may also be a sign of an incompletely formed spinal cord (what we call spina bifida) or a situation where the spinal cord is stuck to tissues around the spine or what we call a tethered cord – although these conditions are quite rare.

How Can You Tell if There is a Problem?

– If you can see the floor of the dimple, that usually means there is no ongoing connection, especially if your child has an otherwise normal neurologic exam.

– Your child’s health care professional will want to do some additional imaging studies if: — You can’t see the floor of the dimple, or — If the dimple is higher up on the back and has near it or over it a tuft of hair or skin discoloration around the pit, or — Your child shows any abnormality of their neurologic exam such as leg weakness suggesting a problem with the spinal cord.

– Imaging could include an ultrasound or MRI to see if there is an open connection that requires surgical repair or an infection in that connection that requires an antibiotic.

– It is important not to have your baby’s bowel movements collect in the pit. Putting a barrier ointment like Vaseline over the pit and keeping it clean will prevent any risk of infection if there is the slightest chance of an open connection with the spinal cord.

Hopefully you’ll find tips like these not to be the pits when it comes to recognizing the simple from the not-so simple sacral dimple.

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Lewis First, MD, is Chief of Pediatrics at The University of Vermont Children’s Hospital and Chair of the Department of Pediatrics at the University of Vermont’s Larner College of Medicine. You can also catch “First with Kids” weekly on WOKO 98.9FM and NBC5.