In normal canine parturition, the female (bitch) goes through three specific stages of labor.  Prior to its onset, her body temperature will drop a few degrees.  (The normal body temperature for dogs is 100.0 to 102.5 degrees Fahrenheit.)  Labor should start within twenty-four hours of the temperature drop.  In stage one, the mother-to-be is restless.  She pants and paces.  The poor girl just can't get comfortable.  During this phase her cervix is dilating.  She is having small contractions that are not visible.  Some first time moms will looks at their sides as if to ask "What's going on?"  

Once contractions are visible, the bitch is in stage two labor.  Puppies are usually born after ten to fifteen minutes of active straining.  They may come out head or tail first.  Either is fine.  Watch closely to see if a placenta (the sac around the pup) is delivered with each pup.  Some females will try to eat this which I do not recommend.  I have seen intestinal obstructions develop from this. 

During stage three labor, any retained placentas are delivered.  Watch closely to make sure this happens.  A retained placenta may cause a life-threatening infection.  Seek medical attention right away if you suspect this occurred.

For further information on whelping please see my upcoming blog post "Canine Labor:  When To Call The Vet".