What information does Macduff reveal about himself that makes Macbeth frightened?

When Macbeth meets Macduff at the king's palace, he learns some crucial information that fills him with fear and superstition. Macduff reveals that he was not born naturally but instead "from his mother's womb / Untimely ripped." This means he was born via Caesarean section, which was considered unnatural and associated with witchcraft in Macbeth's time. In addition, Macduff declares, "I bear a charmed life, which must not yield / To one of woman born." With this statement, Macduff implies that he is immune to harm from anyone who was born naturally.

These revelations shake Macbeth to his core because they contradict the witches' prophecies. The witches had told him that he would be safe until "Birnam Wood come to Dunsinane," and that "none of woman born" could harm him. Therefore, Macbeth initially believed himself invincible. However, Macduff's supernatural circumstances suggest that the witches' predictions may not be as infallible as Macbeth had assumed. As a result, Macbeth becomes afraid of Macduff and realizes that his power and security are no longer secure.