Spay Cat to Prevent Surprise Pregnancy, Uterine Infection and Mammary Cancer

By Lee Pickett

January 2, 2020 4 min read

Q: Stormi, my new kitten, will be an indoor-outdoor cat. I know she needs to be vaccinated and eventually sterilized, but isn't it better to let her have one litter of kittens before that?

A: Cats live longer, healthier lives if they don't have kittens and are sterilized between 2 and 6 months of age. Later sterilization increases the risk of mammary (breast) cancer, the third most common cancer in female cats.

Mammary cancer is aggressively malignant. By the time it's discovered, it has already spread to the other mammary glands, lymph nodes and lungs. Surgery and chemotherapy are ineffective, so survival is less than a year.

The risk is decreased by sterilization, called spay surgery in females. Cats spayed by 6 and 12 months have 91% and 86% decreased risk, respectively, of developing mammary cancer. Waiting until the cat is 2 years old decreases risk only 11%.

Have your veterinarian spay Stormi as soon as her vaccination series is complete, or she may surprise you by going into heat. Typical heat behaviors include rubbing, nuzzling, rolling, crying, yowling, raising her behind and spraying urine.

Female cats are seasonally polyestrus, which means they are in heat during seasons with increasing and long daylight, and they have multiple ("poly-") heat cycles ("-estrus").

As daylight increases in January, female cats as young as 4 months go into heat, and they continue to have weeklong heat cycles through the end of summer. If the cat isn't bred during her first heat, she goes into heat about a week later. This pattern of recurrent heat cycles makes it seem as though the unspayed cat is always in heat.

Cats are pregnant for two months, giving birth during the warm months of spring, summer and fall. It's not uncommon for a female to have two litters a year.

Yet another reason to have Stormi spayed is to prevent uterine infection, which strikes 1 in 4 unspayed cats.

You can avert unpleasant heats, uterine infection and mammary cancer by having Stormi spayed soon.

Q: I hear conflicting stories about whether antifreeze is toxic to animals. It's time for me to change my car's coolant, and I have two dogs who like to "help" with my projects. How careful must I be?

A: Standard antifreeze contains ethylene glycol, or EG, which is extremely toxic. Every year, EG poisons 10,000 dogs and cats, untold numbers of wild animals — and 5,000 humans, including hundreds of children.

EG tastes sweet, so your dogs will be attracted to it. Keep them away from the area when you are changing your antifreeze, because just 3 tablespoons can kill a 25-pound dog. A cat can die after walking through a puddle of EG and licking it from her paws.

Even dilute antifreeze is toxic, so if you spill it or see the telltale yellow-green puddle on the ground, don't hose down the area. Instead, sop up the antifreeze with paper towels, rags or cat litter. Seal the contaminated material in plastic bags, and discard them in a secure trash can.

EG causes kidney failure. Clinical signs include vomiting, diarrhea, increased drinking and urination, disorientation, loss of coordination, rapid heartbeat, trouble breathing, seizures and coma. Without immediate treatment, EG poisoning is fatal.

A safer alternative is propylene glycol, or PG, antifreeze. Popular brands are Sierra and Prestone LowTox. PG is added to foods, medications, artificial tears and cosmetics, although at very high doses, even PG can cause problems. So remember that while it's quite safe, it is still a chemical that should be handled cautiously.

To keep your dogs and others safe, be very careful when you drain and dispose of your EG antifreeze, and consider replacing it with a much safer PG antifreeze.

Lee Pickett, VMD, practices companion animal medicine in North Carolina. Contact her at

Photo credit: cocoparisienne at Pixabay

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