Key takeaways: Most sacral dimples are small, shallow, close to the buttock crease, and harmless. Dimples that are large, deep, higher up the back, or come with a tuft of hair, skin tag, birthmark, or bump may need an ultrasound to check the spinal cord.
A sacral dimple is a small indentation in the skin at the lower back, just above the buttock crease. It’s common and usually not a concern.
Simple Sacral Dimples
A dimple is usually considered “simple” and low risk when it is:
- Small (less than about 5 millimeters across).
- Located low, within about 2.5 centimeters (1 inch) of the anus.
- In the midline.
- You can see the bottom of it.
- Not accompanied by other skin findings.
Simple dimples generally don’t need imaging.
From the author
From First Breath to First Birthday is my month-by-month guide to your baby’s first year, written as a NICU and postpartum nurse. My book starts in the first hours after birth and walks you through every newborn check and the weeks that follow.
Features That Need a Closer Look
Your baby’s doctor may recommend an ultrasound of the spine if the dimple:
- Is larger or deeper.
- Is higher up on the back.
- Isn’t in the midline.
- Is one of multiple dimples.
Or if there are other skin markers over the lower spine, such as:
- A tuft of hair.
- A skin tag or tail-like growth.
- A birthmark, hemangioma, or discoloration.
- A lump or fatty bump.
These can sometimes be signs of a hidden problem with the spinal cord, called occult spinal dysraphism or a tethered cord.
Ultrasound
Spinal ultrasound works best in the first months of life, before the bones of the spine harden, often before about 4 to 6 months. Later, an MRI may be needed.
Care
Simple dimples need no special care. Keep the area clean during diaper changes.
Talk to your baby’s doctor if: you notice a dimple with any of the features above, the dimple drains fluid, or you see redness or swelling. Also mention any later weakness in the legs, unusual foot shape, or problems with bladder or bowel function.
The Bottom Line
Most sacral dimples are harmless. Larger, higher dimples or those with other skin findings may need a spinal ultrasound in the first months.
Want more support for your baby’s first year? My book, From First Breath to First Birthday, is available on Amazon.
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Sources
- American College of Radiology. ACR Appropriateness Criteria: suspected spine malformation or occult spinal dysraphism (child). https://www.acr.org
- Kucera JN, Coley I, O’Hara S, Kosnik EJ, Coley BD. The simple sacral dimple: diagnostic yield of ultrasound in neonates. Pediatr Radiol. 2015;45(2):211-216.
- Lewis ML. A comprehensive newborn exam: part II. Skin, trunk, extremities, neurologic. Am Fam Physician. 2014;90(5):297-302.
This article is for general education and is not a substitute for individualized medical advice. Always talk with your baby’s health care provider or your own provider about your specific situation. If you think your baby or you may have a medical emergency, call 911.
