Your dog is in heat
You love your dog, but you think it would be neat to have a litter of puppies. Your vet never told you not to breed her, and never suggested spaying her, so you figure it'll be okay. You ask around, and find a male the same breed as yours. If you're lucky, the person you've found is a professional breeder who will honestly evaluate your dog and advise you as to whether or not she should be bred. If you aren't lucky, you've ended up with a pet owner who knows absolutely nothing about breeding or worse, someone who is representing themselves as a "breeder" and will breed anything for money. Either way, you will not have a source for help or advice should something go wrong. Here's what can go wrong when your dog is in heat: your dog escapes and gets bred by the neighbor's mixed breed, the neighbor's dog digs under the fence and breeds your dog, she bleeds on your light colored sheets, she bleeds on the carpet, she bleeds on the furniture, she escapes and gets hit by a car, she develops an infection and has to go to the vet.

You take your dog to be bred
If things go smoothly, the two dogs will like each other and will "tie" with no difficulties. Here's what can go wrong at this point: your dog is afraid of the male, the male is afraid of your dog, your dog snaps at the male, the male has no interest in your dog, your dog isn't in "standing heat" yet so will not let the male near her, you've waited too long and your dog is on her way out of heat, your dog picks up hookworms from the stud owner's yard, your dog gets fleas from the stud dog, your dog contracts brucellosis from the stud dog, the dogs tie but then your girl freaks out and runs under the bed dragging the male with her.

Your dog is pregnant
Hopefully your dog is pregnant by a nice specimen of the same breed. She is current on her vaccinations, and you had her checked for parasites prior to breeding. She's eating well, has no discharge, and is getting plump. Here's what can go wrong during pregnancy: infection, miscarriage, puppies grow too big for her to deliver.

Your dog is in labor
If things go as they should, you're home, you're awake, and your dog has a puppy every half hour until she's done. You're organized, and have already set up a cozy bed for her, in a quiet but well-lit area of your home. You have all the necessary equipment on hand, and know how to cut umbilical cords. If you were concerned about the delivery, you had x-rays taken a few days before, so you know exactly how many puppies she will have. If things don't go well, here's what can go wrong: first puppy jams and dies (other puppies can't come out), first puppy comes out okay but second puppy jams, puppy comes out but isn't breathing, puppy is deformed but alive, dog is pushing but no puppies are coming out, dog becomes exhausted and stops pushing, puppies are very tiny and weak, one or more of the puppies are stillborn, puppies are premature and lungs can't function, puppies don't look like either parent, your dog is in the dirt under your house having the puppies and you can't reach her.

Your vet is closed
It's midnight and your dog is in trouble. Here's what will make the situation worse: you can't get your vet on the phone, there is no animal emergency clinic near you, there is an emergency clinic but they want at least $200. upfront, you don't have a charge card, you've been quoted $450.-$500. for a c-section and you can't afford it, you go to bed and let nature take its course - when you get up, your dog is dead.

You have a litter of puppies
Assuming the delivery went okay, you now have a nice litter of puppies. You think you're out of the woods, but you're not. Here's what can go wrong: your dog has no milk, your dog has eclampsia and can't get up, your dog has mastitis and has to be taken away from the puppies, your dog develops an infection and has to be spayed, your dog has no interest in the puppies, some of the puppies are weak and won't nurse, puppies are dying and your kids are upset, you're up and down all night bottle feeding puppies, you have to take time off from work to bottle feed puppies.

Your puppies are 6 weeks old
They all lived, and they're eating food. You've enjoyed taking care of them, but you know soon they'll be old enough to go to new homes. Here's what can go wrong now: puppies are thin and have dry coats because they have hookworms, puppies are bloated because they have roundworms, puppies have fleas, puppies get tapeworms from the fleas, puppies have earmites, puppies get sick, your child steps on one of the puppies and breaks it's leg, puppies are eating you out of house and home, puppies are going to the bathroom everywhere, puppies are doing a lot of damage, some of the puppies look like their father was something other than what you expected, puppy gets out and gets hit by a car right in front of your house.

Your puppies are 8 weeks old
The litter is weaned and you can legally sell them to new homes now. Here's what can go wrong: you haven't taken them to the vet yet so they're full of worms, they weren't vaccinated at 6 weeks and all come down with parvo, you call your vet to schedule health certificates and are told they will cost $50. per puppy, your vet discovers several of the puppies have congenital defects which will require surgery, you try to sell the puppies without health certificates and get reported to Animal Control, you put ads in the paper and nobody calls, you sell a puppy but it gets sick the next day - the new owner expects you to pay the vet bill, you advertise the puppies as "AKC" registered but you didn't register the litter because you didn't know how.

"Humm", as my vet used to say when something went wrong, "So you want to be a dog breeder?"