When you are ready to have your baby, you'll go through labor. Contractions let you know labor is starting. When contractions are five minutes apart, your body is ready to push the baby out. During the first stage of labor, your cervix slowly opens, or dilates, to about 4 inches wide. At the same time, it becomes thinner. This is called effacement. You shouldn't push until your uterus is fully effaced and dilated. When it is, the baby delivery stage starts. Crowning is when your baby's scalp comes into view. Shortly afterward, your baby is born. The placenta that nourished the baby follows.