fertile vs postnatal

fertile

adj
  • Capable of developing past the egg stage. 

  • Of land, etc.: capable of growing abundant crops; productive. 

  • Of one's imagination, etc.: active, productive, prolific. 

  • Not itself fissile, but able to be converted into a fissile material by irradiation in a reactor. 

  • Capable of reproducing; fecund, fruitful. 

postnatal

adj
  • (of a mother) after giving birth 

  • after being born, of or pertaining to the period immediately after birth 

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