The reasons why cats have lumps in their belly after giving birth:

1. It may be a sign of the cat’s milk being blocked. When the female cat at home appears in this state, the owner can help the female cat deal with the lumps. First, use Apply a warm towel to the hard lump in the female cat's belly, and then use both hands to gently knead the female cat's belly to squeeze out the excess milk from the female cat's belly and the hard lump will disappear.

2. You may have been injured, resulting in a hard lump in your stomach. It will get better after a period of observation.

3. It may be a congenital defect in the cat, such as a hernia. If the hernia has not grown, you can leave it alone. If the hernia is growing, a hernia repair surgery is required.

4. It may be tumor cells and needs to be sampled and sent to a specialized laboratory for examination.