Empty your bladder, prop yourself up with pillows, and read or have a snack, then go back to sleep naturally.

http://www.babycenter.com/406_is-it-safe-to-take-sleeping-pills-during-pregnancy_1246859.bc

But if it's just an issue of being uncomfortable at night or routine insomnia, I don't recommend sleeping pills. Instead, empty your bladder, prop yourself up with pillows, and read or have a snack, then go back to sleep naturally.