Laser treatment for a PWS is tuned to the vessels just underneath the skin. It shrinks the vessels temporarily. The length of time before the vessels begin to dilate again is individual. It depends on a lot of factors. This is why you'll hear of some who only have 5 or 6 treatments initially and then can go a couple of years before they need to maintain the vessel size again....and on the other end will hear of some who have many treatments initially and require maintenance yearly. It really depends on how extensive the malformation is.
Laser treatment does have a positive cosmetic outcome in regards to the color for a lot of people treated. It's kind of the perk for dealing with it at all. But it's definitely not a cosmetic procedure when it is used to treat a vascular birthmark. It does prevent all of the things that Corinne mentioned, and that should be the concerns that affect anyone's decision to treat or not. But we're human...and we want our children to have a positive self esteem. I, myself gauge the success of my son's laser treatments by the lightening of color, and the several weeks of a more symmetrical face. :
Truthfully...it means I will have less questions from other people to answer for a while. And at this point is the only defense we have to keep his hypertrophy at bay.
Ben's birthmark is also light in color, and actually was not even visible when he was a young infant. It was there, but the vessels were still to small to actually have enough blood in them to make the entire birthmark "appear". As he aged and the vessels continued to dilate, the birthmark grew darker. Basically, the vessels involved in the PWS will usually continue to dilate throughout life. And as they dilate, the blood pools in the vessels. This can cause the birthmark to darken, thicken, cobble, etc. The birthmark will grow with him also. The older he gets...the larger the area to treat.
At 9 months old, with a small birthmark, it's hard to picture. And perhaps these things will never happen. It's common for some of these things to happen during puberty and in adulthood. Sometimes younger children will have these problems...depending again on the individuals birthmark.
I see it both ways in my household. My son Ben is 4 years old, and the reason that I'm active on these boards. He has a light right side of face PWS, but has both tissue and bone overgrowth as a result...at quite an early age. The vessels are fertilizing the surrounding area...so to speak. My husband is 34, and has a couple of PWS birthmarks. Face, arm, and back. They haven't changed a bit since I've met him...and he's got so many freckles (LOL), I never even noticed them until the geneticist pointed them out to me. He has no complications from them.
It's very individualized...which makes these decisions about treatment frustrating. I am an advocate of early treatment. You'll find that's a common thing here. But it's still a decision only you can make. The best part is that at 9 months old with no complications, you definitely have the time to consider your options, do some research, and make sure that any doctor you choose for treatment is the right one.
Oh...and I apologize for the book. :
Didn't mean to get so long winded.