Cats do not understand pregnancy in the human sense, but they can sense that something is different about a person during pregnancy. They detect changes primarily through shifts in scent caused by pregnancy hormones, changes in body temperature, and alterations in behavior or routine. Cats have a highly sensitive sense of smell, about 14 times stronger than humans, allowing them to notice these subtle changes before others may. As a result, cats may respond with altered behavior such as increased affection, protectiveness, curiosity, or even stress depending on their personality and how the pregnancy affects household routines.
In summary, cats can sense that their owner is pregnant through physical and behavioral changes but do not comprehend the meaning of pregnancy as humans do.