Yvonne, for whatever reason, I've always heard it is more common in boys.
My ref says 1 in 150 males and 1 in 750 females. It tends to be familial
and is seen primarily in white, first born males. (Isn't that
interesting!?) I believe it is lots less common in BF babies, but I don't
know a source on that. Sincerely, Pat in SNJ