You may want to breed your dog, but maybe you aren't quite ready yet. Birth control for dogs isn't as well-established as it is for humans because pet owners tend to rely on spay surgery to keep their dog puppy-free. There are dog contraceptives on the market, but the only effective natural birth control for your dog is abstinence.
The Estrus Cycle
Depending on her breed, size and health, your dog will come into heat every six months. If she's a smaller dog, she may experience three heat cycles a year, compared to a giant breed dog that goes into heat every 12 to 18 months. On average, a dog will stay in heat for 2 to 3 weeks, and because sperm can survive in her reproductive tract for a week, she can conceive at any point during her estrus.
Effective, But Not Natural
There are a few options to prevent pregnancy in dogs. Spaying is the most popular method, however it's permanent, which isn't appealing if you want to breed your dog. There are canine contraceptives, available in tablet or injectable form, which shorten or prevent a dog's estrus cycle. However, canine contraceptives are generally used for the short-term since they come with a variety of risks. As well, if you're looking for a natural birth control method for your dog, these drugs, such as mibolerone, aren't considered "natural" birth control.
If you're the adventurous type and you wondered how your pup would look in a pair of underwear, you can try one of the many doggie diapers or britches on the market to guard your girl's virtue. The problem with diapers is they often fall off the dog, though if you're able to keep them on your pup, it will keep her from making a mess in the house during her cycle. Ultimately however, diapers and panties for dogs aren't a reliable means of keeping a determined male suitor away.
Unfortunately, there is no natural magic pill to give your dog that's been proven to be safe and reliable for preventing pregnancy. If you can't or won't spay her, the only thing to do is confine her for the duration of her heat cycle. If she's not wearing a diaper, or she's able to get out of her diaper, it's a wise choice to keep her in a space that's easy to clean, such as a tiled room. Your dog's behavior will likely change when she's in heat. She may become more pushy, whiny and restless, pacing and panting, perhaps acting aggressively with other pets. If she's too forceful with other pets in the house, you may want to isolate her from them, or crate her for part of the day. If you aren't going to breed your dog, talk to your vet about your concerns about spay surgery to learn if it might be okay for your dog.