Why isn't my 4-year-old dog going into heat? Is she too old to breed?

She may be extremely clean and you might not notice when she is in heat. If you intend to breed her I suggest you have her examined by a theriogenologist or veterinarian specialised in dog breeding . She may not be cycling due to ovarian cysts, or may be missing ovaries, or have hormonal problems.

Your female is too young and you should not breed her yet. Dogs should not be bred until they are 2 years old because they are physically and mentally immature. Additionally, Yorkies have a few health concerns so both parents need to be screen before breeding. Any dog that is bred should be with the intention to contribute the best genetics to the breed. Not because they are nice dog, are pure bred or because they are cute. Here is a link about Yorkies and the conditions that require screening. Look at the care section under the Health tab: https://www.akc.org/dog-breeds/yorkshire-terrier/ Wait another year for the female and have both screened. I hope this helps and please feel free to post any additional questions.

Female dogs don't actually stop having [heats](https://www.petcoach.co/article/anatomy-and-function-of-the-reproductive-system-in-dogs). This is because as they get older, they do not always show the external or behavioral signs that they are actually having a heat, this can sometimes be referred to as a ‘silent heat.' It is important to remember that even though your dog may not be showing signs of being in season that she could still get pregnant if mated by an intact male dog. Ideally, you should consider having her [spayed](https://www.petcoach.co/article/spaying-ovariohysterectomy-the-benefits-in-dogs). There may also be an undiagnosed hormonal disease or ovarian disease present that stopped her cycling. In order to make sure it is not a serious condition you should have her checked by a veterinarian. It is possible that it is a harmless reason, but it is also possible that there is a serious underlying condition.

She may be in a false pregnancy cycle or have an infection in her uterus due to hormonal changes. Temperamental can be related to this or it may be a sign of pain or dominance at her age. The best thing to do is have a vet check her for an infection or a false pregnancy. From there you can discuss having her spayed to prevent future heat cycles so you no longer have to worry.

Yes, it can be normal. Often times though, they have gone into heat, you just didn't notice. Some dogs keep their vulva clean so you don't notice any bleeding. If you are worried then I suggest you take her to your vet for a breeding soundness examination.

It is unusual that Maria hasn't gone into her first heat at her age, and it's possible that she has had a heat but it was a silent heat. I'd recommend a check up with the vet for this problem. It would be rare if she was born without a uterus, but it could be possible. Only a vet can diagnose this. I'd make an appointment for her this week. I hope this helps!

There are many things that could cause infertility. You would need to get her to a veterinary reproductive specialist to get a diagnosis; they will let you know if it can be corrected. ( https://vcahospitals.com/know-your-pet/infertility-in-female-dogs ) If she cannot conceive you should have her sterilized to prevent further problems like pyometra and mammary (breast) cancer.