The only sign of a capillary malformation is the birthmark itself: a reddish-pink stain that usually appears on the face or neck, but can show up anywhere in your child’s body. A capillary malformation can darken in color and your child's skin can thicken as she ages, and will grow as your child grows.

Tiny growths called "blebs", which bleed easily and are sometimes painful, can appear from the malformation. A capillary malformation can also be painful if it’s covering a deeper vascular anomaly.

Rarely, a capillary malformation can be a sign of an underlying abnormality. For instance:
A capillary malformation over the spinal column can sometimes be associated with spinal abnormalities.

A capillary malformation can cover a deeper vascular abnormality involving your child’s arteries, veins or the lymphatic system, such as Klippel-Trenaunay syndrome.

Very rarely, if the stain covers part of the forehead and upper eyelid, your baby should be evaluated for neurological problems, as it could be a sign of a very rare condition called Sturge-Weber syndrome. Only eight percent of kids with a facial capillary malformation have neurological problems.