menstrual cycle vs monthly

menstrual cycle

noun
  • The recurring cycle of physiological changes in the uninseminated females of some animal species that is associated with reproductive fertility; especially the cycle in a human woman. 

monthly

noun
  • The menstrual period. 

  • A publication that is published once a month. 

adj
  • Occurring every month. 

adv
  • Every month. 

How often have the words menstrual cycle and monthly occurred in a corpus of books? (source: Google Ngram Viewer )