Abortion is "in the eye of the beholder". I don't believe the dilemmas around it will ever be resolved, especially with the rise and popularity of anti-abortion political factions and personalities in the United States. Worldwide, the Catholic Church is highly influential. It is most known for an anti-abortion stance, but there are many other religions against abortion as well, such a evangelical protestantism and Mormonism. I lived/worked in the most Mormon (LDS) region of Idaho, north of the Utah border for a year. I recall that no abortions were allowed or even allowed to be discussed by any hospital in that region. If someone needed an abortion, they would have to go to another state, unless perhaps it was allowed in Boise, which I don't know. Boise and Coeur D'alene, Idaho, are less LDS influenced, especially Coeur D'Alene in the Panhandle. Again, whether that is right or wrong is "in the eye of the beholder".

Traveling for an abortion is a global phenomenon:

"In the US, about 8% of abortions are performed on women who travel from another state.[110] However, that is driven at least partly by differing limits on abortion according to gestational age or the scarcity of doctors trained and willing to do later abortions.[citation needed] Thousands of women every year travel from Northern Ireland, the Republic of Ireland, Poland, and other countries where elective abortion is illegal, to Britain or other countries with less restrictive laws, in order to obtain abortions.[111][112]"
http://en.wikipedia.org/wiki/Abortion

This is where abortion becomes a medical, and especially medical ethics issue:

"Abortion has a low risk of maternal mortality except for abortions performed unsafely, which result in 70,000 deaths and 5 million disabilities per year.[2] Abortions are unsafe when performed by persons without the proper skills or outside of a medically safe environment. An estimated 42 million abortions are performed annually with 20 million of those abortions done unsafely."
http://en.wikipedia.org/wiki/Abortion

So half of abortions worldwide are unsafe.

Another issue of medicine and criminal law is attacks on physicians performing abortions, as well as other crimes associated with the anti-abortion movement, such as:
Murders; attempted murder, assault, and kidnapping; arson, bombing, and property crime; anthrax threats
http://en.wikipedia.org/wiki/Anti-abortion_violence

I rest my case. Yes, it is a medical issue, but so much more.
Many folks are reluctant or afraid to openly discuss abortion, so let's see who answers your question, Maurice. As for me, I would prefer not to have an abortion, and would be sad about the loss of a child if I had one in my life. I know there are many infertile couples who are waiting for newborns to adopt, so that is an option as well. But a life and death situation would certainly result in my decision to go forward with an abortion. Fortunately I never had to face the dilemma. I certainly do not force my views on others; it is deeply personal.

It is interesting, but I seem to view abortion more from the woman's perspective, as well as that of the abortion performing physician. I am glad Steve brought the zygote as human being into primary focus as well. Laws on homicide do seem to depend on perception of "humanhood", so are much framed by societal values.
Two questions:
1. How is an elderly person with advanced Alzheimer's Disease, or someone who is brain dead but kept alive with machines, both of whom may have no more or less of "humanhood" than a zygote without memory and identity? Why are the adults kept alive, including by extraordinary means, but humans at conception often are not? What gives each kind of life value?
2.. What is the difference between religious and moral values, or are they the same? Can one be moral and accept abortion? Every one of us was a zygote at one time. Think about it.

Kim,
Excellent points. Especially morality vs religion. I am unable to draw a clear intellectual line between the two. To me, religion feels more like a system of personal beliefs most or many of which are not capable of being logically dissected and analyzed. They depend upon faith. Religious values are passed onto successive generations of believers. My religion tells me abortion is "wrong". Morality on the other hand is typically subject to rigorous intellectual analysis by philosophers.

To me, as a man with no children, there is a huge difference between the perspective of the woman and the physician. For the woman, an abortion decision would seem to go directly to her sense of what it means to be a woman. To a physician, I would think it is less personal and more clinical. At least I would hope so. I don't want a Christian Science leaning surgeon bringing her religious beliefs to me on the operating table.

Personhood, humanhood? To me, the common denominator is self-awareness. Not the potential of self-awareness nor the history of self-awareness. The ability to know now that I am me. Absent that, neither the person nor the human exist. What exists is an organism which might as well be a plant.

And goes.....
Even the concept of "humanhood" versus "personhood" is not agreed upon, as already noted.
There are just issues in human discourse that are impossible to resolve. Perhaps every view has legitimacy. Unfortunately, the diversity of views still allows the disabilities and deaths of zygotes, fetuses, women, and physicians.

Here is an overview of US states with laws regarding fetal homicide, incorporating definitions of "humanhood" and "personhood" in many cases:.

http://www.nrlc.org/unborn_victims/Statehomicidelaws092302.html

Here is Canadian commentary supporting fetal homicide law:

http://network.nationalpost.com/np/blogs/fullcomment/archive/2007/11/22/margaret-somerville-defending-fetal-homicide-laws.aspx

Here is a Canadian abortion rights argument against a
fetal homicide law:

http://www.arcc-cdac.ca/fetal_homicide_law.html

And a Member of Parliament's tabling of the "Unborn Victims of Crime" Act:

http://arpacanada.ca/index.php/issuesresearch/41-pro-life/112-unborn-victims-of-crime-bill-introduced-action-item

I think both woman and fetus need protection in the commission of a crime. I am wondering, however, if fetal homicide laws can also be applied to physicians who perform abortions, which is a criminalization of a medical procedure, an ethically questionable action, at best.
There have been some high profile homicides of pregnant women in Western Canada the last few years. Killing a woman whether pregnant or not, should not be lumped in with a abortion.