I'm copying and pasting an old entry from my webjournal that touched on this subject. But before that, I'd just like to note that murder only becomes murder when there is premeditated intent to kill. Sex is a procreative act. And could NEVER be seen as murder. Interfering with this conjugal act by attempting to reduce the chances of procreation is not just morally ambiguous, but morally reprehensible. One of God's greatest miracles is the creation of life, and doing anything with the intent to hinder His miracles. . .well. . .I surely wouldn't want to risk it.
"I once was a fetus. Who will deny thissurely a fetus was what I once was? But now if the right-to-life (understood as the right not to be deprived of life by human decision unless one has deserved such deprivation through a crime that one has been duly convicted of) is an essential property of me, part of what makes me who I am, then since I was a fetus, that fetus was I, and hence it also possessed the right-to-life, as the right to life is an essential property. Alternately, as is reasonable, being a person is an essential property of me. I could not be myself without being a person. Whatever is not a person is also not identical with me. But I was once a fetus. Hence, that fetus was a person, because I was that fetus and being a person is an essential property of me. But it is a conceptual truth that all persons have a right-to-life. Hence, so does the fetus.
At one point of my life. I was nothing more than a cell. A single cell. Microscopic. Would you have stripped me of my right to life? Would you have prevented me from living the first 9 months of my life in my mother's womb? Would you justify doing so merely by noting that I was composed of a single cell? That was me. I'm all grown up. No person has a right to end the life of another unless it is for the protection of others and no other means of detainment are possible.
Let us imagine a situation involving two people, Dick and Jane. Long story short, Dick rapes Jane against her will. Her right to choose was brutally ripped away from her by Dick though his actions. The end result? Emotional trauma for Jane most likely, and me. There I am, in Jane's womb. Through no decision of my own, mind you, but through the brutal act of rape which was in essence the denial of another person's(Jane's) right to choose to engage in sexual activity. That is lost. She can never regain it(For that instance). Now I exist. She becomes aware of my presence in her. She did not want me, she does not want me. I am an inconvenience, and it is NOT her fault that I am there. But I live nonetheless.
We are taught from a VERY young age to turn the other cheek. You will recall the maxim "Two wrongs don't make a right." See how that can apply to this situation. A wrong has been committed against Jane. I am the result. Jane's solution is either to A. allow me to live, recognizing my right to it, or B. wrong me, in a way infinitely more sinful than Dick wronged her. I would be no more. I would never take a breath, might never even develop lungs. I would never see the world outside of Jane's womb. My mortal existence, gone. Not at the command of God, who should be the final arbiter in determining when we are through in this world, but at the request of Jane, whose "problem" can only be solved by ridding herself of me.
What if zygotes possessed cognition? What if they possessed the inherent knowledge that at ANY moment their life could be taken away from them by the very people whose parents DID allow them to live out their life. The terror that would incite within us would be nearly unbearable. Scary thought.
*I can't finish this without touching on the spiritual aspect of this. If you're not interested, skip over it. Otherwise, don't worry it'll be short.*
So Jane bears her cross. She can either take it up, as Jesus has commanded us, or throw it at His feet in a loud refusal of "It's too heavy!" Jane has been forced to bear the sin of another. One man, Dick. It is his sin that she must bear. Wow, when you think about the nature of what sin truly is, DEEP and grievous offense against God Himself, that is a HUGE cross. And just think, Jesus bore a cross greater than any that he would give us. He bore the sins of ALL humanity, he sweat BLOOD for our sins, was scourged, humiliated, beaten repeatedly, spit on, tortured, scoffed at, and all at the hands of that which He himself created. Such suffering he endured for the sins of all of us. We are called to follow in His footsteps, and specifically for Jane, to bear the sin of Dick, just as Jesus bore her sin, and Dick's, along with all of us.
It's a hard thing to do. But the path we are called to walk is a narrow one. But the rewards, infinitely greater in magnitude than the hardships we must endure by keeping on that road."