Although it may seem like dogs can turn up pregnant in the blink of an eye, it's actually a fairly complicated process. Just ask any breeder who has repeatedly tried and failed to produce a litter from her champion bitch; sometimes things just don't go according to plan. Successful dog breeding is all about the timing, so take a closer look at the biological issues behind the process.

Heat Cycle Indicates When to Breed

Estrus

Simply put, estrus is a bitch's fertile time, generally referred to as a heat cycle or "season". The first heat cycle typically takes place between six and nine months old, but breeds that mature more slowly may not experience a first heat until twelve to eighteen months of age.

Cycle Length

A normal heat cycle lasts approximately three weeks. In the beginning stages, known as proestrus, a bitch's vulva begins to swell, and you may notice her licking herself more than usual. Male dogs will also begin sniffing her more as her hormones begin to produce a scent that signals she is becoming ready to breed.

Stages of Heat

• Week One - Once the vulva begins to swell, the bitch will begin to produce a bloody discharge. The amount will vary from one bitch to the next, so it may or may not be noticeable.

• Week Two - Sometime around nine to twelve days, the color of the discharge lightens to a pinkish-tan color, and it's usually around this time, referred to as estrus, that the vulva softens and eggs are released from the ovaries. At this point, you may notice your bitch flirting with other dogs; this is a sign she is ready to accept a male's advances.

• Week Three - If the heat cycle is allowed to continue uninterrupted, by the third week, the discharge begins to look bloody again. The amount will trail off until the cycle has concluded with anestrus.

Yearly, Bi-Yearly or Quarterly Cycles

On average, a healthy bitch comes into season every six months. However, this can vary, and some bitches only cycle once a year while others come into season on a quarterly basis. Quite often, bitches that come in quarterly are not fertile every season.

Signs That It'sTime to Breed

Look for these signals that your bitch is ready to be bred:

• General flirty/affectionate behavior

• Tail held high and flagging

• Pushing up rear when petted on the back

• Willingness to stand and present vulva

• Color change in discharge from red to pinkish-tan

The Mating

Breeding usually takes place naturally without any human intervention beyond introducing the dam to the stud. However a little direction may be required if one or both of the dogs involved have never been bred before. Typically, the male dog will become very excited when introduced to a receptive bitch, sniffing and licking at her vulva. Very quickly he will mount her from behind and begin to thrust. When all goes as nature has designed, he will penetrate the bitch's vulva; this causes two glands directly behind the penis to swell considerably.

In response, the bitch's vulva will clamp around this swelling; this is referred to as a tie, and it's the moment when the dog and bitch become "stuck" together. This period typically lasts from fifteen to thirty minutes, and it is at this point that sperm are being delivered to waiting eggs.

If the breeding has been successful and the bitch conceives, she will deliver her pups between 58 and 63 days later. You can easily find your dog's due date by consulting a canine pregnancy calendar.

Time Will Tell

Once a breeding has been completed, it will take some time to find out if it was a success. You'll be able to tell if a litter is on the way a lot sooner if you learn to spot the signs of pregnancy.