lying-in vs pregnancy

lying-in

noun
  • The final stages of pregnancy; accouchement. 

  • A period of postpartum confinement, typically a month or longer, formerly common in Europe and still practiced in some parts of the world. 

adj
  • of, or relating to childbirth or postpartum confinement 

pregnancy

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

  • The progression of stages from conception to birth. 

  • The period of time this condition prevails. 

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