bb has a birth mark at the ankle area. quite big patch. like blue black. will it be visible as they grow up? afraid will be ugly for girls...

hmm.. I think it will help if you just treat it normally and simply tell your child that it is a birthmark and she is born with it. This will help her learn to acknowledge it as just a part of her and hopefully not be too conscious about it in future (just in case it doesn't fade).