There are several possible signs of labor, and only a few definite signs.  Discuss these signs with your childbirth professional and make sure you receive instructions on when to notify him/her you are in labor, and when to actually go to the hospital or birthing center.  

Possible signs of labor (may or may not be signs of labor):

• Backache that comes and goes.
  
• Frequent soft bowel movements.
  
• Menstrual-like cramps.
  
• Nesting Urge.

Preliminary signs of labor (signs of progress, but still early labor or prelabor):

• Bloody show, loss of mucus plug.
  
• Leaking of amniotic fluid.
  
• Nonprogressing contractions (stay about same length, strength & frequency)

Positive signs of labor:

• Progressing contractions (longer, stronger, closer together)
  
• Gush of amniotic fluid.  (Even if labor doesn't start, most caregivers will want you to deliver within 24 hours of your water breaking.)