As the male and female bodies are aroused, they also set the stage to increase the chances that fertilization and pregnancy will occur. (Read more here about some of the physiological miracles that occur as a husband and wife come together sexually—but be aware at the outset that this material is explicit). This is the third point we should consider. Only a heterosexual union can produce a baby. Infertile couples certainly do exist, but they do not negate the general rule that when one man and one woman come together and share themselves with each other intimately and sexually, the way is paved for conception, pregnancy, and the eventual arrival of a child. The “one flesh” union, therefore, isn’t just about a couple’s coming together and uniting their bodies sexually; it’s also about the “one flesh” person that can and often does result from the sexual experiences they share. As Ryan Anderson has said, “The lovemaking act is also the life-giving act. The act that unites a man and a woman as husband and wife is the same act that can make them mother and father. This begins to tell us something about what the marital relationship is ordered toward.”1
1Ryan T. Anderson, Truth Overruled: The Future of Marriage and Religious Freedom, (Kindle Edition: Regnery, 2015), loc. 411.