Is it only in one thigh? My niece has this and my SIL was told by her ped that it is something called an amniotic band. It is caused in uterus and sometimes it can be severe enough to cause deformed limbs. Her ped said that as she gets older, it should become less noticable and it really wasn't a cause for concern because hers isn't too bad. Hope this helps.
NOOO idea why it would be concerning.... both my girls had about a gazillion extra creases in their legs because they were FAT babies! was there anything in particular about the crease, did the health visitor SAY anything about it? i know sometimes if i forgot to clean between the fat rolls, sometimes they'd get some extra lint that could get irritating, or occasionally dry skin built up in there, which could also get irritating.... could it have been something like that? or was it like a "your baby is too fat, look at these creases that shouldn't be here..." or was it just a "hmmm, he has an extra crease..." with a frown and no elaboration (HATE that!)???
those are the only ideas that came to my mind, sorry!
My DD had this at her 2 month check up with the doctor. The pediatrician asked if she was breech and when I told her she was, she said she should have a hip ultrasound. Sometimes if either baby was breech or in a funny position while in utero, I guess it can deform one or both of the hips. But my DD had the ultrasound and she was normal. But I bet that's why it was noted. I don't know if this is an issue if your child wasn't breech, but I'd ask your pediatrician just to be safe.
DD, conceived after infertility (3rd IUI), Born July 2007
Baby #2, conceived naturally! EDD March 16, 2009
Why my dd (who is almost 18 months old now) had her first few checkups, the doctor would check her legs front and back to make sure her creases were even and symetrical. Because they were, he didn't talk to much more about it. However, I briefly remember him saying that would show if she was having any problems while developing, etc.