posterity vs unborn

posterity

noun
  • All the future generations, especially the descendants of a specific person. 

unborn

noun
  • Unborn offspring collectively. 

  • A single unborn offspring at any stage of gestation. 

adj
  • Not yet delivered; still existing in the mother's womb. 

  • Not yet born; yet to come; future. 

  • Existing without birth or beginning. 

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