Your pup can't get pregnant if she didn't have her period, a term that's better known in dogs as a heat cycle. Even if you miss her heat cycle and she appears pregnant, she may not actually be.
In most cases, you'll notice a bloody discharge soon after your pup's heat cycle begins. While some dogs have lots of discharge, other canines bleed only a tiny bit. The VCA Animal Hospitals website notes that you might not notice the discharge in some dogs, particularly those with dark fur. That can lead you to believe that your little girl never went through her heat cycle when she actually did. However, you should notice increased urination and possibly marking behavior while she's in heat.
Even if you missed your pooch's heat cycle, she would still need to be around an intact male dog to become pregnant. If she was not but still shows signs of pregnancy -- such as nesting, restlessness, nausea and enlarged mammary glands -- she might have a condition known as false pregnancy. Only your vet can make that diagnosis, so make an appointment with him if she's displaying pregnancy symptoms.
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