A miscarriage is the loss of a pregnancy before the 20th week of gestation. It is a common occurrence in dogs, affecting about 10-20% of pregnancies. There are many different causes of miscarriage in dogs, including:

Infection: Bacterial, viral, or parasitic infections can all lead to miscarriage in dogs. Brucellosis, canine herpesvirus, and neospora caninum are some of the most common infections that can cause miscarriage.
Hormonal imbalances: Low levels of progesterone, the hormone that helps to maintain pregnancy, can also lead to miscarriage. This can be caused by a number of factors, such as illness, stress, or nutritional deficiencies.

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