Causes of weak hind legs and big belly of kitten after going out:

Kitten has weak hind legs and big belly after going out. It may be due to cat-borne disease, which is mostly transmitted from cat to cat. Ascites will appear in the abdomen. When there is a lot of ascites, it can be clearly seen with the naked eye. The cat's belly is swollen and wider than the normal body width. You can feel the water fluctuations by touching it with your hands. If your cat’s abdomen is obviously distended, it’s best to take your cat to the hospital for examination.

Methods to determine if a cat is pregnant:

1. Determine whether your cat is fertile, observe mating behavior and understand the cues of a cat in estrus.

2. Observe whether the cat’s nipples become enlarged and pay attention to the cat’s body shape.

3. Observe nesting behavior.