For some people, it comes down to a perspective on these "big" things, as well.
For example, I believe I'm not ultimately in charge of what happens in my life. I'm supposed to be responsible, treating my body as a temple-while relying on God's wisdom to guide my choices, as well as His wisdom to choose for me the outcome He sees fit-as only He sees the big picture.
Others believe in some part of divinity or destiny or fate..some believe in karma, etc.
Therefore, in my belief and faith, I am charged with a great responsibility of doing all I can to protect the life growing within me through eating healthfully, living a healthful life, having faith and praying. I believe, ultimately, that no matter what choices I make, the fate of this child (and all my children, born or not) is in God's hands....but that doesn't excuse me from making educated, informed and healthful choices.
It's a great responsibility when we understand (and most here do) the gravity of what it means to be a parent. For me, it means I've been charged with the biggest responsibility in this world-to care for and raise a family. I do not turn this responsibility over to doctors (in the case of our day-to-day health and illnesses, and now I am turning this way with birth) unless God shows me that it's too great of a situation for me to handle.
Anyway, I know that was a big rant! I apologize! I am trying to be respectful of all aspects of birthing and how outcomes are affected by health...sometimes, as PP have said, we can do all things right, be healthy, plan for safety and a future for our babes, and have empty arms. This is true of m/c (which I've had) or birth loss. Sometimes, as we also know, the crack addicts, alcoholics and irresponsible take home a baby-or CPS does. Sometimes, these things just don't make sense. For some people, it's because we see that we don't have the entire big picture-though that doesn't offer the comfort, but it's an explanation for the unexplainable, some like me believe in.