Why Lady Macbeth Couldn't Concieve

The hope of Lady Macbeth and Macbeth to one day have children and have their kids rule Scotland is now crushed due to Lady Macbeth being an evil witch. Lady Macbeth can't conceive due to the evil magic she possesses it is too strong of power to produce anything because her powers are made to kill so it automatically will kill it in her stomach. Another thing is her body transforms from a witch to Lady Macbeth so during that switch the baby would be neglected oxygen from Lady Macbeth which would also cause it to die.  They were both heartbroken when they found out they couldn't conceive a child to love and maybe one day they would rule Scotland. Lady Macbeth after hearing that news and was already planning to kill King Duncan she told the dark spirits to turn her breast milk sour and take her womanly instincts away from her. After the news she felt she had to kill King Duncan so that Macbeth could be king and then she would be queen. Having kids was one out of the hopes they hoped for the most.