Reading online, week at 5 my little baby's heart is beating and circulating blood. Woah, how great is this? According to baby-gaga this is what is going on: "Growth is now largely focused on their little head, which is starting to develop much more rapidly than the rest of their tiny body. This is because their amazing brain is undergoing some very crucial and rapid development in order to effectively regulate their heart rate, blood circulation, and other vital functions. As for the rest of their miniature body, what were simple limb buds last week are limb flippers this week and the tail is more expressed. Amazingly, within a mere five weeks your little miracle is already developing the rudimentary forms of their liver, pancreas, lungs, stomach and nasal pits while their little heart is already increasing its circulation. Your baby is now a whopping 4-6mm in length."
That is some intense stuff... Be careful, little baby. Your libel to fall over with that big o' head of yours. ;)