There are 5 "stages" of a Reproduction Management record, Heat, Mating, Gestation, Whelping and Birth. You should create a new record for each heat cycle and use one record to follow the heat cycle all the way to the birth of puppies.
You can create Reproduction Management records from it's tab or the Dame's record using related lists. Filling it out from the Dame's record will auto-fill the Dame field.
From Reproduction Management Tab
You can enter a new record from the Dog Locations Tab.