My daughters big toe nail has grown out cracked since birth. Now she is almost 3 and no one can tell me why...?

I would like to know why my daughters big toe nail grows out split down the middle. The whole nail splits and its been like that since birth. No one can give me an answer.My daughters big toe nail has grown out cracked since birth. Now she is almost 3 and no one can tell me why...?
I don't know why but I would take her to a podiatrist if you haven't already seen one, you may just need to keep the nail really short so it doesn't crack.