Abstinence is already a form of pregnancy-prevention. Not having sex would be as well wrong as aborting, because it "prevents pregnancy".
And that cannot be considered as a reasonable because it's not realistic to make any action that does not cause pregnancy as ethically controversial as abortion. Purely an unpractical approach that can't survive the challenges of reality.
A sperm cell and an egg cell on their own are not a individual member of the human species because they have no complete and/or unique DNA set. Therefore preventing them to merge is not bringing up a conflict of murdering a human being and therefore is less ethically controversial than an abortion. Ergo there is a difference between abortion and pregnancy prevention.
Contraceptives such as condoms prevent pregnancy by preventing the egg from being fertilized. Contraceptives such as birth control use hormones to prevent ovulation from occurring. Abortion is destroying the fetus or egg after the egg has been fertilized.
Put another way, abortion can not happen pre-pregnancy, and pregnancy-prevention cannot occur post-pregnancy.
It all depends on when you perceive life to begin. If you believe that life begins at birth, then it is difficult, but not impossible, to compare terminating a pregnancy to preventing one. However, if you believe that life begins at conception or in the womb, as I do, then it becomes a contrast between preventing life and taking life away. Ultimately, I feel that pregnancy prevention is far more morally acceptable, and also healthier for the body, than abortion
Birth control is preventing unwanted babies from suffering at the hands of people that don't want children while abortion is the execution of a fetus by people that were irresponsible and don't want children. Kind of harsh, but so is reality. Use the birth control and there will be no need to kill a fetus.
I've spent a ton of time thinking about stuff like this, and I've realized that if you consider abortion as prevention of life, and consider prevention of life equal to murder, you therefore could apply that to pregnancy prevention. So while they fall together on the spectrum of prevention as murder, there is a difference in what goes on in the literal, physical process.
An abortion is the ending of a pregnancy, while pregnancy prevention is taking steps to keep a pregnancy from happening. Just by definition they are different things. . . . . . . . . . . . . . . . . . . . . . . .
The ultimate reality of both systems is that they are in place to prevent the natural occurrence relative to the behavior so whether it be coitus interruptus all the way up to the IUD or long-term medications the goal is exactly the same which is child prevention. An abortion is basically the same thing after contraception therefore any moral high ground had is merely animalistic in nature since when preventative measures fail we do not tend to criticize damage control.
Our entire society is built off of this; we have warning labels on everything as preventative and when the actions do come to pass we have response teams, procedures, etc.