The red, flat patches known as hemangiomas, or strawberry marks, are the most common growths on babies' skin, occurring in up to 2.5 percent of newborns. More common in premature babies and female infants, most hemangiomas — which can develop anywhere on the body — show up within the first three to four weeks of life, though some are present at birth.

Hemangiomas start out as flat red patches and, with time, may enlarge and thicken, potentially continuing to grow for 10 months to a year. They then enter a phase of inactivity, which is soon followed by the last phase, when they begin to shrink on their own. About half of all hemangiomas will be gone by the time a child is 5 years old, and 90 to 95 percent will be gone by the time she's 10.

Treatment is usually unnecessary unless the hemangioma bleeds frequently or is somewhere it could interfere with general bodily functions — such as near an eye or on the mouth. If your baby has a hemangioma that is a problem for any reason, your pediatrician or pediatric dermatologist can discuss possible treatments with you.