The images do not look like the embryo, except that tehy're shaped similary, like a rectangle or an elipse, their lenght is bigger than their width, that's all. You can there's also a significant amount of differences between the creatures. What particulary strikes me is a giant blood sucking hole on a leech's head, that an average embryo lacks...
And besides, leeches are not the only thing to resebmle an embryo. There's also worms, snails, various sea creatures, chewed gums...
And as I said, a leech and an embryo are so vastly different that a similar shape means nothing at all.