Sacral dimples occur in about 5% of neonates and are the most common cutaneous sign of spinal dysraphism (incomplete closure of the neural tube during early embryogenesis, leading to spinal or bony abnormalities). Simple dimples are defined as midline depressions in the dermis that are less than 5 mm in diameter and within 2.5 cm of the anus. Larger lesions ("atypical dimples") and those above the gluteal cleft have been associated with spinal dysraphism.

Both sexes are equally affected. There are no differences reported among ethnic groups.