"In the early 20th century, however, to "make love" took on a new sense that Oxford defines this way: "orig. U.S. To engage in sexual intercourse, esp. considered as an act of love. Freq. with to, with."

The dictionary's first written example of this usage is from Sex, a 1927 play by Mae West: "Jimmy embraces Margie LaMont and goes through with her the business of making love to her by lying on top of her on a couch, each embracing the other." (The OED citation is from a 1997 collection of Mae West plays edited by Lillian Schlissel.)

We'll end with an example from George Orwell's 1934 novel Burmese Days: "Why is master always so angry with me when he has made love to me?"

From: http://www.grammarphobia.com/blog/2012/12/making-love.html