Also to Susanna, Tall_Timbers, Magenta, daisyseesthesun and Mem,
I introduced this topic because I hope to help "open the eyes of the blind" (IS 42:7) by sharing my own history. I knew very little about fetal development when I was in my twenties, and "pro-choice" sounded like a good option so I was a "birthist", but when I was confronted by pictures of a seven-month-old fetus in the womb and a seven-month-old premature but viable baby outside the womb, I realized that geographical location is not a valid basis for defining personhood because there is no qualitative change that occurs at birth, merely a difference in the mode of breathing and feeding.
Thus, I was led to consider the crucial question: when does a developing fetus become a human person with the God-given right to civil life so that to kill it is murder and warrants punishment? The conceptionist viewpoint is certainly right that a qualitative change occurs when the chromosomes in the egg and sperm are united, and learning about fetal development should enable birthists to realize that the advent of personhood definitely occurs by the seventh month or viability, when a premature baby is frequently able to survive.
Are there any changes between conception and viability that might reasonably/logically be viewed as indicative of the beginning of personality? There is one possibility: the counterpart of the basis doctors use for determining when an adult person no longer is alive. This basis is brain death or the absence of certain brain wave activity detected by an electroencephalo-gram (EEG). We might call this stage “sentience”, referring to the level of brain activity which indicates the fetus has brain life and is therefore a person, who should be granted the civil right to life. If our best definition of sentient death is the cessation of these brain waves, then it is logical and consistent to view sentient life as beginning at least when these brain waves are detectable. Thus, I think every open-minded and truth-seeking person should agree that the fetus becomes sentient and a legal person at least by that stage of development.
This is only a partial solution, but it is a big step in the right direction toward no abortion except in order to save the life of the mother. It recognizes that a gray area still exists from conception until sentience, so people may still reasonably disagree about the status of the fetus during this period, which may change as science improves. This view permits most forms of birth control. Implementing this solution requires educating every post-pubescent person about fetal development until society develops a new consensus that when a fetus becomes sentient, abortion is a type of murder and should be punished appropriately.
Love in Christ, GWH