Many Routes To Pro-Choice
Schraub's evolution occurred through becoming more pragmatist, in the sense of adjusting his moral commitments to each other without holding any firm foundational principle. In the process of this, the fetal personhood concern lost the power to sway his position -- because of uncertainty about when personhood occurs, the strong clash with the value of the mother's autonomy, and a J.J. Thomson-inspired questioning of whether saving a life always trumps other concerns.
My own position, on the other hand, started out more pragmatist. Fetal personhood swayed me only because I had made a conscious decision to avoid, as much as possible, having an opinion on abortion because I found the abortion debate to be hugely unproductive and thus a waste of my energy when I could be actually changing someone's mind on another issue. Given my lack of attention to resolving the existence and weight of fetal personhood, I felt like I might as well err on the side of caution and lean pro-life. Later, however, I realized that I had committed to a strong moral principle -- a form of preference utilitarianism -- that gives a definite standard for personhood*, and I had acquired enough factual information about fetal development that I couldn't honestly claim not to be able to draw the conclusion that abortion is, at least in most cases, morally justifiable.
* I've been meaning to write a longer post about the fact that I actually find the whole Kantian/Christian framing of moral questions in terms of beings who do or do not have "personhood" or some other form of inherent moral value -- and thus the whole "considerability" debate in environmental ethics -- to be a distraction. My reasoning doesn't say "fetuses don't have preferences, therefore fetuses are not moral persons, therefore fetuses don't have inherent value, therefore it's not wrong to kill them." Rather, I cut out the middle-man and say "fetuses don't have preferences, therefore it's not wrong to kill them."