I just wanted to share a video link that I just found. Premature babies are much more likely to have hemangioma birthmarks. Millie, a 34 weeker had/has (it's almost gone) quite a large one on her left thigh, Joe has a big one on his tummy and several small ones dotted around, and Harry probably has around 30 in total, luckily all relatively small and mostly on his body where they can be covered.
This is an amazing, amazing video which shows how quickly they grow and the dramatic effects of having it removed. Stick with it through the talking at the beginning.