1) There is a tradition of modesty, and “Lashon Nekia”, clean speech which means that some talk about these issues is constrained by euphemism such as “and the Man knew Eve his wife”.2) On-going performance of this activity is legally discussed as an obligation from husband to wife known as Ona, time. This is not limited to reproduction, as it applies beyond child bearing years.
 This issue was touched on in my post “http://torahforsociallyawarehasid.blogspot.com/2010/11/shame-pride-striving-case-of-reuben.html” Based on Rashi on Beresheet 49:2, Beresheet Rabbah, Zohar, Bereshith, Section 1, Page 176a, cited by Rabbi Ari Kahn, http://rabbiarikahn.com/index.php?option=com_content&view=article&id=69:reuven&catid=41:vayishlach&Itemid=56 .
 Rabbenu Bchai, Tazria 12:7
 Daat Zekainim Mbaalei Hatosafot on Leviticus 12:8
 Rashi Leviticus 10:17, beginning with words Laseat et Avon Haedah, two examples of a sin offering that were not for the purpose of atonement
 Minchat Chinuch discussion relating to Mitzvah 168