Why is Mary's pregnancy important in the story Lamb of the Slaughter?

Mary's pregnancy in "Lamb to the Slaughter" serves as a critical element that shapes her character and motivations. It adds depth to her emotional state and heightens the stakes of her actions, particularly when she kills her husband, Patrick. Her pregnancy evokes sympathy from the reader and influences her subsequent behavior as she cleverly manipulates the situation to avoid suspicion. This element underscores themes of betrayal and survival, making her transformation from a devoted wife to a cunning figure more striking.