Let's look again at 2 Corinthians 10:3, 4, 5:
King James Bible
For though we walk in the flesh, we do not war after the flesh: (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;
In particular, I want to look again at the word translated "strongholds" (Ochuroma a castle, stronghold, fortress, fastness; anything on which one relies, of the arguments and reasonings by which a disputant endeavours to fortify his opinion and defend it against his opponent) and the word translated "imaginations" (Logismos: a reckoning, computation; a reasoning: such as is hostile to the Christian faith; a judgment, decision: such as conscience passes).
Think of a stronghold as an entrenched idea that is holding the person prisoner. Today's stronghold is the personal/physical. And in this case, the stronghold is the idea that we "own" our bodies.
Much of the modern resistance to chastity comes from men's belief that they 'own' their bodies—those vast and perilous estates, pulsating with the energy that made the worlds, in which they find themselves without their consent and from which they are ejected at the pleasure of Another! -- C. S. Lewis, "The Screwtape Letters"
Think about it -- how much control do you really have over your body? It goes about its business -- metabolizing, bringing in oxygen and putting out carbon dioxide -- without any input from you whatsoever. Did you choose your sex? Your height? Whether you have a light frame or a heavy one? Whether you have a fast or slow metabolism? You couldn't halt the process of maturation, and you can't stop the process of aging. And you can't avoid death. The more you know about what goes on in your body, the more you realize that you're just a tenant in a vast estate that operates with very little of your say-so.
Sure, you could kill your body with a bullet to the brain or enough carbon monixide. You can tend it in ways that make it healthier or less healthy. But really, you have very little control at all. And if you're pregnant when you didn't intend to be, you're faced with proof that your body produced and released an ova without your say-so, and somebody else's body cranked out a load of sperm without his say-so.
You might rail against this powerlessness by destroying the fruit of that union, but in doing so, you're in a way admitting how little control you really have.
You're a tenant, like it or not. A steward. You have a lot of control over what you do with your body -- whether you use it for good or evil, or whether you sit around like a slug and do nothing. But ultimately you're responsible to the Maker of that body for what you did with it.