I'm going to assume that your baby is due about now (if this is happening earlier than 37 weeks of your pregnancy, we'd worry about prematurity). When your body starts getting ready for labor, several things happen. The baby usually "drops" into the pelvis, and it becomes easier for you to breathe. Your cervix, which is the bottom part of your uterus, starts to get thin. Doctors and nurses call that "effacement." Think of the cervix as a big, thick piece of dough you're getting ready to make into a pie. The cervix is thick like that. When labor is going to begin soon, the cervix starts to get thin, just like that dough when you start to roll it. As the cervix gets thinner, it also starts to open. Doctors and nurses call that "dilating." When the cervix is as thin as it can possibly be, it is 100 percent effaced. When the cervix is as wide open as it possibly can be (so the baby's head and shoulders can fit through), it is 10 centimeters dilated. At the moment, your cervix is about half as thin as it will be when you give birth, and not quite half as open as it will be when you give birth. It's impossible to say when active labor will begin for you, but I'd guess fairly soon! Hope that helps!