Macbeth has leaned into the prophecies of the witches early in the play because they tell him things that he wants to hear. They seemingly continue to predict that he deserves to be King, which emboldens him to commit regicide. However, in his final meeting with the witches, their predictions aren't so favorable. One of the witches tells Macbeth that "none of woman born / shall harm" him; unfortunately, Macbeth misinterprets this prediction (IV.i.87-88). Macbeth wants to believe that his ambitious quest will serve him well, so he believes that the witch is telling him that no one can possibly harm him. After all, aren't all people born of a woman? Macbeth thus replies, "Then live, Macduff. What need I fear of thee?" (IV.i.89).

Filled with new courage, Macbeth clings to the idea that he deserves to be King. When he meets Macduff in the final scene, he boldly tells Macduff what the witches have said:

Let fall thy blade on vulnerable crests;
I bear a charmèd life, which must not yield
To one of woman born. (V.vii.14-16)

Imagine Macbeth's shock when Macduff casually replies,

Despair thy charm,
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother’s womb
Untimely ripped. (V.vii.17-20)

Instead of being born vaginally, Macduff was "ripped" from this mother via a caesarean section delivery. One has to imagine that this was not a common method of delivery when Shakespeare wrote the play during the early 1600s. A mother would have no real anesthesia as someone performed this surgery on her, which means that she would have endured incredible pain in order to deliver the baby. Likely, such a delivery would have resulted in maternal death.

It is a stretch in our society to imagine that people considered a caesarean delivery as not being "born," but this idea reflects the way that medicine has changed our lives in the past four hundred years.

When Macbeth visits the three witches for the second time in act 4, scene 1, they offer him seemingly favorable prophecies in the form of several apparitions, which fill him with false confidence and embolden him to behave recklessly and impetuously. Although the first apparition tells him to "Beware Macduff," the second apparition instructs him to "Laugh to scorn / The power of man, for none of woman born / Shall harm Macbeth" (4.1.81–83).

Macbeth misinterprets the prophecy by taking it literally. Since every man is born of a woman, Macbeth believes that he is protected from all men and becomes overconfident. He does not consider that there is a double meaning to the prophecy, which concerns the various ways women can give birth.

Later on, Macbeth comes face to face with Macduff during the final battle and discovers that Macduff was not born naturally of a woman but was "Untimely ripped" from his mother's womb. Macduff's comment means that he was not born naturally from his mother's birth canal but was delivered by caesarean section. Macduff's mother probably experienced various complications giving birth and was forced to have a caesarean section. Once Macbeth discovers that he was misled by the three witches, he curses them and refuses to fight Macduff. Macduff responds by instructing Macbeth to surrender, but Macbeth decides to challenge him.

In Act 4, scene 1, Macbeth returns to the witches to consult them about his future. It is at a time when he has become paranoid about his security and wishes to hear their assurances. The witches call up different apparitions and the second apparition informs him:

"Be bloody, bold, and resolute; laugh to scorn
The power of man, for none of woman born
Shall harm Macbeth."

This statement emboldens Macbeth and he says:

"Then live, Macduff: what need I fear of thee?"

It is ironic that Macbeth refers specifically to Macduff here, since he discovers to his utter dismay later, that Macduff was not "of woman born".

When the two confront each other on the battlefield in Act 5, scene 8, Macbeth warns Macduff:

"Let fall thy blade on vulnerable crests;
I bear a charmed life, which must not yield,
To one of woman born."

Macduff replies:

"Despair thy charm;
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd.

Macduff informs Macbeth that he had not been naturally born, i.e. he did not pass through the birth canal but was prematurely removed (ripped) from his mother's womb - so it could not be said that he was 'born' in the true sense of the word. It was an unusual and unnatural act. It could be that Macduff's mother was incapable of bearing her son by natural means which compelled the surgeons of the time to perform, what we call nowadays, a Caesarean Section.

Macbeth is shocked and dismayed by this information and realizes that he had been fooled by the witches. They had deliberately misled him - an example of the equivocal and paradoxical nature of their predictions. He declares:

"Accursed be that tongue that tells me so,
For it hath cow'd my better part of man!
And be these juggling fiends no more believed,
That palter with us in a double sense;
That keep the word of promise to our ear,
And break it to our hope. I'll not fight with thee."

When Macbeth refuses to fight, Macduff commands him to surrender but Macbeth prefers not to. They fight and Macbeth is killed.

Macduff was not born of woman - he was delivered by Caesarean section.

The witches tell Macbeth that no man born of woman can harm him.  Sounds pretty good - all men are born of women, right?  All men, all people, came from a woman.

However, the term "born" literally refers to the process of going through the birth canal.  Macbeth believes he is safe, until he meets Macduff, who the witches told him to watch out for.  Macduff proves that it is possible for man not to be born of woman:

Macduff: Tell thee, Macduff was from his mother's womb Untimely ripp'd

In other words, he was pulled directly from his mother's stomach, not "birthed" or "born". 

This is the final example of how Macbeth has misinterpreted events, twisting what he has heard to suit his own purpose - but in the end, his misperception has sealed his downfall.