Most puppies are born without incident, but in any delivery, there's always the potential for canine labor complications. Owners must distinguish between what is normal during delivery and what is a red flag. Keep all of your veterinarian's contact information handy in case of labor problems, and be prepared to take mother -- and any delivered puppies -- to a veterinary hospital in case of emergency.
Dystocia, the formal term for canine birth difficulties, runs the gamut from mild to severe complications. It can mean the dog is pregnant for more than 70 days, or that labor hasn't started within 24 hours after an expectant dog's temperature drops below 100 degrees Fahrenheit -- the standard way of predicting the beginning of labor. Labor complications can result from a variety of factors, including an oversized puppy unable to get through the birth canal, a badly positioned puppy and canine uterine issues.
During the first stage of labor, your dog exhibits behavioral changes. She likely displays "nesting" activity -- digging about to find a comfortable place to deliver -- and becomes restless or clingy. By this point, you should have a suitable whelping box available, where she's likely to start nesting. A strong, low, wide cardboard box lined with old towels and blankets should suffice. In labor's second stage, which can start hours later, the mild contractions of the first stage turn into the strong contractions of delivery. If your dog enters the period of powerful contractions but no puppy arrives within half an hour, she's likely experiencing dystocia. While breaks between puppies are common, they shouldn't last more than four hours. Contact your vet if either of these situations occur. (ref 1,3)
If you see an abnormal discharge from the mother dog's vulva, get in touch with the vet. That includes either a green discharge with no puppies arriving for at least two hours or vaginal bleeding that lasts more than 10 minutes. The green discharge, called uteroverdin, indicates the placenta may have already separated from a puppy. Vaginal bleeding could result from a number of serious issues.
While any dog can experience dystocia during delivery, some dogs are at higher risk than others. If a dog has had trouble having puppies previously, it's more likely she will again. First-time mothers are at greater risk, as are older mothers and obese mothers. A dog carrying only one or two puppies is at risk because her hormone levels might be insufficient for labor induction. Flat-faced or large-headed breeds, such as the bulldog, often require a planned Caesarean section because of the puppies' head size relative to the size of the birth canal. Your vet will weigh the risk factors for your particular dog and recommend a course of action.