Years and years ago, I remember reading in a book on AmE usage that the phrasal turn a baby creeps before it walks was to some extent more common to AmE than to BrE, which preferred exclusively the "crawl" version.
What I would like you to tell is if it would sound sort of weird to hear someone say today in the US that a child "creeps" before walking and running (see Synonyms) rather than it crawls.
Also, what's the story to those terms? How did "to crawl" come to prevail and supersede "to creep" to describe the way a baby moves around?
As with a plant, so with a child. His mind grows by natural stages. A child creeps before he walks, sits before he stands, cries before he laughs, babbles before he talks, draws a circle before he draws a square, lies before he tells the truth, and is selfish before he is altruistic. Such sequences are part of the order of Nature... Every child, therefore, has a unique pattern of growth, but that pattern is a variant of a basic ground plan. (Bigge & Hunt, 1962, p. 166)
My impression is that "to creep" instead of "to crawl" for how a baby moves around might have made a lot of sense in the old days if you consider the way babies were dressed back then. Think also of Swee'Pea's outfit in Popeye the Sailorman cartoons.
Besides, here is a article I just found on Parent.com, which asserts a difference between saying "to creep" and "to crawl."