post-partum vs postpartum

post-partum

adj
  • Pertaining to the period immediately after childbirth. 

postpartum

adj
  • Of a mother: after giving birth (often defined as within 30 days after childbirth). 

noun
  • The period immediately following childbirth. 

adv
  • After giving birth. 

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