In most cases, your dog's body shouldn't go into heat for a few months after pregnancy, but individuals can have irregular cycles. The fact is, how long after pregnancy a dog has her next period, or goes into estrus or heat, varies widely.
Most female dogs experience a first heat cycle at the age of 6 months. Unless spayed or pregnant, they'll go into heat every six months for the rest of their lives. Dog heat cycle's breaks down into proestrus, estrus, diestrus and anestrus.
During the nine-day proestrus, a dog starts bleeding but she won't allow males to breed. During estrus, another nine-day cycle, she's fertile and allows mating. Diestrus lasts two to three months, whether or not a pregnancy is involved. The hormone progesterone takes control of her reproductive organs. If she's pregnant, her gestation is about two months. During anestrus, her body sends no sex signals.
During the anestrus stage, your dog's ovaries remain inactive, and she isn't interested in attracting males. Anestrus lasts between one and six months. That's a wide range, but figure three to four months for the average dog. If your dog's anestrus falls on the low end of the scale, she could go back into heat shortly after weaning her puppies.
If you decide to have your dog spayed after her puppies are weaned, you must schedule the surgery before she goes into heat again. Many vets either won't perform a spay when a dog is in heat or will charge more for it. Because her reproductive organs are swollen, the operation becomes more complicated and time-consuming.
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