pregnancy vs propagation

pregnancy

noun
  • The period of time this condition prevails. 

  • The progression of stages from conception to birth. 

  • The condition of being pregnant; an instance of this. 

propagation

noun
  • the multiplication or natural increase in a population 

  • the act of propagating, especially the movement of a wave 

  • winning new converts 

  • some degree of success in the spread of propaganda 

  • the dissemination of something to a larger area or greater number 

  • the elongation part of transcription 

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