When she tells Michael she’s leaving him, and he refuses to accept this move, Kay drops the bomb:
Oh, Michael. Michael, you are blind. It wasn't a miscarriage. It was an abortion. An abortion, Michael. Just like our marriage is an abortion. Something that's unholy and evil. I didn't want your son, Michael! I wouldn't bring another one of you sons into this world! It was an abortion, Michael! It was a son Michael! A son! And I had it killed because this must all end! I know now that it's over. I knew it then. There would be no way, Michael... no way you could ever forgive me not with this Sicilian thing that's been going on for 2,000 years.
But is she bluffing?