due date vs menstruation

due date

noun
  • The date on which a pregnant woman is expected to give birth. 

  • The date by which a book (or other item) borrowed from a library must be returned. 

  • The date by which a task is supposed to be completed. 

  • The date of payment in financial arrangements. 

menstruation

noun
  • An instance of menstruation, the part of each month during which a fertile woman menstruates. 

  • The periodic discharging of the menses, the flow of blood and cells from the lining of the uterus in unfertilized females of humans and other primates. 

How often have the words due date and menstruation occurred in a corpus of books? (source: Google Ngram Viewer )