The dog heat cycle can vary dramatically. Dogs go into heat on average twice a year, but some dogs may go into heat three times and many larger breeds only once annually.
The cycle lasts an average of 12 to 21 days but can be as short as a few days or last as long as four weeks. A female's first heat cycle will usually occur sometime between 6 months to a year, although it may occur as early as 5 months in smaller breeds and as late as 14 months in larger breeds.
HOW LONG ARE DOGS IN HEAT?
The short answer is approximately 2 to 3 weeks.
The heat in dogs usually lasts around 18 days, but can often last anywhere from 12 days to 28 days. We commonly say a bitch takes one week to come into heat, one week to be in heat, and one last week to come off heat. This is a rule of thumbs and is extremely approximative.
HOW MANY HEATS DOES A DOG HAVE?
The short answer is that small breeds go on heat every 4-6 months, medium breeds every eight months, and large ones every year or more.
However, this often varies especially in the beginning, as it can take some dogs a year and a half or two years to develop regular heat cycles. Small dogs are known to come into season more frequently, as much as three or four times a year sometimes. On the other hand, giant breeds (ie. Great Danes and St. Bernards among others) tend to go into heat every 8 to 12 months.
On average, female dogs cycle into heat every six months.
WEEK ZERO TO ONE
Your dog mated and now…nothing. No shooting stars, no big signs, she acts casual like nothing has happened. Her estrogen levels decline but the pregnancy hormones have yet to click in. Life carries on as normal, and so should she.
On days 8 to 14, the fertilized eggs make their way to the uterus for implantation. You may notice behavioral changes in your dog that represent the first signs pregnancy. For example, she may become moody or more affectionate.
The pregnancy hormone, progesterone, starts to rise. First, in our canine pregnancy timeline, you may notice her coat becomes more plush and glossy, as the hair enters a growth phase all at the same time. If she’s going to get moody or sleepy, now is the time, but she may act as normal. No need to increase the size of her food until Week 6! Overfeeding and weight gain in early pregnancy increase the risk of birthing complications.
On days 15 to 21 your dog may begin to display mood swings, appetite changes, and breast tissue development. At this point, implantation has taken place and the embryos begin to develop.
Watch out for that first physical sign of pregnancy, pinked-up nipples. This is where her nipples enlarge, become more obvious, and take on a rosy glow. It’s a tad too early to be certain she’s pregnant – so don’t hold your breath. She’s fine to exercise as normal, just don’t go mad, especially in hot weather.
On days 22 to 28, the fetuses can be felt in the uterine horns around day 28, and can also be seen by ultrasound. The spinal cords are developing, and the fetuses are beginning to grow facial features. Your bitch's uterus will shortly fill with fluids to protect the fetuses. After this, it will be weeks until the puppies can be felt again. Also, your dog's appetite will likely increase, so offer her more of her food.
Exciting times and the first chance to confirm pregnancy. The vet can now see developing fetuses on an ultrasound scan. The tiny pups now have a spinal cord and are developing facial features. But don’t be tempted to feel her belly for the babies; Rough handling could damage the womb and lead to miscarriage.
On days 29 - 35, the fetuses develop their sex organs and begin to look like actual puppies. The leg buds lengthen and develop toes. Your dog's belly will begin to look noticeably swollen as the pups take up more space. With less room for full meals, it's time to begin serving smaller meals more frequently.
From day 28 a blood test will confirm pregnancy. Also, there’s a window of opportunity between days 28 – 35 when a vet can feel the pups before they become cushioned in the fluid. The female can still exercise if she wants to, but don’t overexert her.
On days 36 - 42, pups continue to grow and pigmentation develops. The eyes now have lids and remain sealed until approximately ten days after birth. Your dog is noticeably more uncomfortable at this point. She may vomit occasionally due to the extra pressure against her stomach. You may also notice clear fluid discharge from her vulva. This is normal.
Ease up on exercise now. Walk her but gently, and let her set the pace. NOW you change her food: Switch from regular food to a puppy food, for the increased calories, protein, vitamin, and mineral content. Her body shape may change, with the hint of a pregnant belly and enlarged mammary glands. Now, entering the final third of pregnancy, she may start to dig or nest. She may suffer morning sickness and vomit occasionally. Also, some females develop a plug of white mucus at the vulvar lips. This is normal. If however the discharge is bloody, discolored, or smells, see a vet immediately.
On days 43 - 49, puppies are well-developed and now begin attaining size in preparation for birth. This is when you can feel puppies move in your bitch's abdomen. Her breasts are well developed as in the image of the pregnant bulldog. The breasts probably contain a bit of colostrum or "first milk." Your dog is noticeably tired and may begin searching for a place to whelp. Time to set up a whelping box.
The puppies now have a skeleton which can be seen on x-ray. Your vet may suggest radiographing the mother to check how many puppies she’s carrying. This information may become useful when she goes into labor and you need to monitor that all the pups are coming out. From now onwards you may get the impression of her belly moving, as the puppies wriggle inside. Her breasts are distinct and can be seen in silhouette The mother tires easily and needs to urinate frequently.
On days 50 - 56, the pups have fur and are now crowded in the uterus. You may notice a lot of activity as they get into position for the coming birth. Your dog may begin digging the bedding in the whelping box. This is natural "nesting" behavior. Allow her to feed freely as she is able.
The pups are well grown and taking up a lot of space in her tummy. The mother may start nesting behavior, which includes digging. Offer small meals but often, as her stomach is compressed. Let her rest and take gentle walks, and give plenty of comfort breaks.
On days 56 - 63, the pups are ready for birth and may be quite still as they rest in preparation for the marathon to come. When your dog is ready to give birth, she may appear uncomfortable and restless or anxious. Time to begin taking rectal temperature readings 12 hours apart. Normal temperature is 100 to 101 F; a drop down near 97 F held for two consecutive readings indicates labor will begin within 24 hours.
For a pregnancy of average length (63 – 65 days) this is the final week. Do puppies move a lot before birth? Yes. The puppies are large and active, causing rippling of her flanks. This makes the mother uncomfortable and restless. Keep an eye on body temperature, as a drop means whelping should happen within 24 hours.
WEEK 10: DAYS 64 - 70
Some breeds, such as French bulldogs, have longer pregnancies than others. Don’t panic, but do contact your vet. Put a plan in place for when to go ahead with a cesarean if the pups haven’t put in an appearance.
VIDEO OF FETAL DEVELOPMENT