There is a cold blooded, chilling nature to the ambition awoken in Lady Macbeth. The lengths to which she says she is willing to go to fulfill a prophecy that she finds self serving go against the understood nature of a woman and the nurturing characteristics of a mother. "I have given suck.." etc.
Upon hearing the prophecy of the Weird Sisters Lady Macbeth pushes her husband and goads him, attacking and doubting his manhood and adequacy in cruel ways until the actions occur. Lady Macbeth is arguably Shakespeare most captivating and intriguing character. Her ability to sink to unplumbed depths so quickly to snare what she believes is her fate would chill any audience. Her descriptions of her capacity to kill babies is shocking and unforgettable.