https://www.reddit.com/r/AskHistorians/comments/28rq87/people_historically_had_a_lot_of_kids_and_also/
https://www.reddit.com/r/AskHistorians/comments/24uikm/when_did_people_start_having_sex_in_private_or_is/
/u/vertexoflife is something of the resident expert on this, I think