Apart from the babies thing, that's still a very interesting question. I bet someone knows the answer, but I wonder if the weight of the earth increases or decreases on average. I'd have to guess it's a net increase from picking up stuff as we move through space, which probably dwarfs the mass of stuff we've sent out (especially if you don't count satellites since they're more or less still tied to earth). I don't think there's anything like natural ejections of matter from earth either.