Crossword puzzle clue is Mammal reproduction is The first letter is an i. What is the word?

Your answer is probably intimacy.

You can solve others questions like this by going to www.yourdictionary.com and typing in the letters you know and a ? for each letter you don't know. I searched i??i???? and received a list of all the Words with this pattern. The Word intimacy comes closest and one of the definitions of intimacy is "explicit sexual intercourse".

Hope this helps!