DTD, walking, rasberry leaf tea, acccupuncture, there are plenty of different ways to get labour going, but I'm pretty sure you could try them all & bubs would still come when ready.
DTD would probably be best as semen does have the prostiglandin thingy's in it to ripen the cervix as cookiemonster said. Sex is actually good for pregnancy. Enjoy it - if it's not too uncomfortable!!