Spaying Dogs and Cats in Heat (Estrus)

puppy at vet office
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You meant to have your dog or cat spayed before she came in heat, but you didn't expect it to come so soon. Dogs and cats have their first heat between 4 to 6 months of age. Although you can ask your vet to spay a dog or cat in heat (also known as estrus), many vets prefer to wait until the heat cycle is over. The size, age, and overall health of the pet are considered as well. If the spay is done while the animal is in heat, the costs are usually a little higher.

Spaying While in Heat

During a heat cycle, the blood vessels that supply the ovaries and uterus are engorged. Additionally, these tissues are more "friable," meaning they may tear more easily than normal and then bleed more. Even tissue not associated with the reproductive organs such as skin, fat, and muscle will often seep more than normal during surgery.

This makes a typically elective surgery more stressful than it needs to be and carries the additional risk of bleeding problems during the surgery or post-operatively. Some veterinarians will not spay a pet in heat and recommend that surgery is scheduled a week or two after the cycle ends.

Some veterinarians are selective about the type of pet they will spay while it is in heat. In general, cats that are in heat are easier to spay than dogs that are in heat. Small dogs are easier than large dogs. Overweight pets are difficult to spay both in heat and not in heat. Anesthesia is riskier for overweight animals too—just one more reason to make sure your pet is not overweight.

Additional Costs When Spaying a Pet in Heat

If a pet is spayed while in heat, the surgery takes longer and additional surgical supplies such as gauze sponges and sutures may be needed. The medications used before, during, and after the procedure may be different than those used on a routine spay. Therefore, the cost of the procedure will be higher to cover the extra time and supplies needed.

Planning Ahead

Dogs and cats are typically spayed by four to six months of age. If the animal is spayed before the first estrus cycle, the chances of mammary cancer are greatly reduced. Spaying at any age eliminates the chance of ovarian and uterine cancers, as these organs are removed during a typical spay. Some animals, especially those at shelters, are spayed and neutered at much younger ages.

The ideal age to spay and neuter is a topic of much debate. Speak to your veterinarian about your specific pet for advice on the best age to spay. Most people agree that it is best to avoid spaying when in heat if possible. Many experts feel that spaying before the first heat cycle is best for the pet. However, recommendations may vary based on the breed and size of your pet as well as current research.

Sometimes an appointment is made in advance or an animal is found or rescued and the estrus status is not known when the surgery is scheduled. If this is the case, speak to your veterinarian about possible risks and added costs of spaying the animal while it is in heat.

Waiting to Spay

If your dog or cat is in heat, you may have decided to wait until she is out of heat for surgery. This reduces the risk of surgery and lowers the cost of the procedure. However, it is important to watch your dog or cat very carefully until she is out of heat. During this time, she may try to sneak out of the house or yard, especially if there are intact males nearby. 

Remember that your dog or cat is very receptive to males at this time. She is hormonally inclined to mate. If she does manage to mate, you may end up dealing with a pregnant dog or a pregnant cat! Then, the question of whether to spay her and terminate the pregnancy, or wait for a litter of puppies or kittens. Avoid adding to the pet overpopulation and do everything possible to avoid accidental mating. Dogs and cats should not be bred unless they are excellent quality purebred animals and you are an experienced, responsible breeder.