Christian Churches are hypocritical in teachings of abortion and euthanasiaWatch
So the reason that abortion and euthanasia are illegal in most countries is due to the fact that they don't abide by the Christian Church teaching of the "sanctity of life". This teaching involves the belief that God has a plan for all of us and he decides when we die and it isn't up to humans and that we shouldn't take this matter into our own hands. However, doesn't that mean that resuscitating someone after they have a heart attack is preserving life beyond its natural span? I mean if God plans for us to die then, why should we interfere?
Yes, Christians believe in the sanctity of life. But the problem is you defined the sanctity of life wrong.
The sanctity of life is the idea that human life is sacred. The biblical basis for this is where it says that mankind is "made in the image of God". People are "image-bearers", and therefore, we (people) have no right to kill another person (without justification).
Sanctity of life is not about God having a plan for us, and if we murder someone, then we are interfering with his plan. The bible teaches that God achieves his plan, through everything that happens. It says that God "works out everything in conformity with the purpose of his will". God has a plan, and it will come to pass, whether we do good or evil.
The issue is that only God has the authority to destroy people, because people are made in the image of God. People are valuable, people are sacred, because they are made in the image of God. I hope this makes sense.
That said, Christians do talk about whether medicine attempts to play God, by pushing back death. I'm a medical student and so this topic particularly resonates with me. I find doctors are often driven more towards working towards "a good death" than simply prolonging life - ie. good palliative care, good pain management, making decisions in advance about the likely benefits of resuscitation etc. That said, we are striving to find more treatments for cancers, we treat pulmonary embolisms and strokes and give patients lifelong medications to prevent future ones, we give lung transplants, liver transplants, bone marrow transplants etc etc etc. All these things push death back. I can see the case for the idea that we are playing God.
It's just not as simple as defying God's will. Nobody can do that.