It says in the Wikipedia article that he was born grasping a blood clot, and that this was a sign of his future as a great leader. Firstly, how does one grasp a blood clot? Secondly, can anyone share information about this belief? Thanks in advance for any information.
A "blood clot" could just mean any bloody, solid-ish thing that's not necessarily a blood clot (like the bits of tissue that can get expelled along with the child during birth). Otherwise, a blood clot is a solid thing, formed when blood congeals together because of clotting factors and whatnot. Think about holding a piece of half-formed jello or toy ooze.
As for the meaning, I have no idea. I hope someone answers this with scholarly sources as a late Christmas gift.
This might also be a good question for /r/askanthropology.
As we've had to remove a number of comments already, can I remind everyone that answers in /r/AskHistorians must be drawn from in-depth scholarly knowledge. Please refrain from speculating.