You'll know you're in it because: Your contractions don't go away, no matter what you do. "False labor can be scared away. If you change your activity, the contractions may stop," says Tonya Nicholson, DNP, CNM, program director at the Frontier School of Midwifery in Dublin, Ga. "True labor contractions progress in strength and frequency."
How long it lasts: The beginning of the first stage of labor can last anywhere from 12 to 24+ hours if it's your first baby. (Second and subsequent labors may be faster.)
How to deal: Notify your partner and make sure your bags are packed. But you might not want to call your family and friends just yet -- birth can still be a long way away!