Canine pregnancy, labor, and delivery can be an exciting time for pet parents, especially when the result is a litter of healthy pups. It can also be a confusing time for those who have never experienced it before. Here's what pet parents need to know about reproduction in dogs. 

Female Dog Heat Cycles

The average adult female dog comes into heat twice per year. However, this may vary by the size and breed of the animal. Small and toy breeds may come into heat three times per year, while larger breeds may only experience one cycle every 12 months. Most dogs experience their first heat when they're between six and 15 months of age. As a general rule, the smaller the breed, the more likely it is for the dog to have their first heat at the early end of the scale.

Bloody vaginal discharge is typically the first sign that a dog has come into heat. Heat typically lasts from two to three weeks. During this time, there is a period of between 10 to 14 days during which the animal can become pregnant. This stage of heat is called "estrus." Signs of estrus include a swollen vulva and a change in vaginal discharge from bloody to thin and watery. Although dogs can become pregnant during any stage of estrus, the most fertile stage occurs when discharge becomes watery.

Puppy Development in the Uterus

A dog's gestation cycle lasts approximately nine weeks or 63 days. Here's a week-by-week breakdown to give pet parents an idea of what's going on while their dog is pregnant: 

• Week 1: Fledgling embryos start high in the uterus but work their way down following successful mating. 
• Week 2: The embryos begin to develop.
• Week 3: The embryos develop a protective membrane surrounding them that will provide them with in-utero nutrition.
• Week 4: The embryos have developed sufficiently for a veterinarian to perform a successful ultrasound.
• Week 5: The embryos exit the embryonic stage and begin the fetus stage. This change signifies a period of rapid growth and organ development. 
• Week 6: As the dog enters the final trimester of pregnancy, the fetuses develop claws, and distinct organs form. 
• Week 7: The fetuses form fur, and the skeletal system starts to solidify.
• Week 8: This is the final week before the puppies arrive. The mother's milk will begin to flow, and the veterinarian may decide to do X-rays. Pet parents need to prepare a birthing area in a warm, draft-free, quiet part of the home. 
• Week 9: The pups can come at any time during the ninth week. Take the mother's temperature three times per day for an indication of when labor is imminent. It should drop to 99 degrees Fahrenheit from a normal temperature of 101-102 around 24 hours before labor starts. 

Stages of Labor in Dogs

Uterine contractors signify the onset of labor. The animal may appear restless, pacing and panting. This stage typically lasts between six and 12 hours. The second stage is the expulsion of a pup from the womb. The third stage is when the mother removes the protective membrane from the pup. Stages two and three generally alternate as individual puppies are born. There are times when pet parents may need to help remove the membrane if the mother hasn't started to do so within about a minute. 

Pre-Whelping Checklist

Pet parents should stock up on the following items to prepare for a successful labor and delivery:

• Clean bedding for after the birth of the pups
• A can of specially formulated puppy milk and feeder — just in case
• A pair of disposable gloves
• Plenty of paper towels

Birth Complications and What Pet Parents Can Do

A strong, healthy mother is the best defense against birth complications. Nonetheless, pet parents should be prepared in case things go wrong. It's important to have the veterinarian's contact information close at hand and call them if complications arise. Typical complications include the mother becoming too tired to continue giving birth, a pup getting stuck in the birth canal, and strong contractions continuing for four hours or more without any pups being produced.   

Pet parents with questions about dog reproduction or other aspects of pet care can contact the Fuzzy Veterinary Team 24 hours per day, seven days per week.