The same remorseless reasoning process that leads Todd Akin and other pro-lifers to oppose rape exceptions leads some exponents of abortion rights to equally bizarre outcomes.
If a pregnancy does not become a person until the moment the child has fully emerged from the mother's womb, then a lot of hideous things become permissible too, including abortions of babies fully capable of life on their own and the sex-selection abortion that has led Nobelist Amartya Sen to calculate that 100 million girls are missing in India and China.
Civilians in the abortion wars try to draw distinctions between cases where abortion becomes more wrong and where it becomes less wrong: yes up to 10 weeks, no thereafter; yes for serious birth defects, no for sex-selection; etc. They are groping for some modulation, some way to translate complicated moral intuitions into rules a society can live by. The belligerents in abortion wars disdain this search for compromise as mere equivocation, a flinching from deeper truths.
Yet the complexity of the abortion issue is also a deeper truth, and so too is the need for people of differing views to find a way to get along with each other.
I've suggested before that the history of the temperance movement might offer a precedent for the abortion debate: the attempt to ban alcohol was abandoned, even as drunkenness was radically reduced. Likewise, we see abortion rates in the U.S. declining, and pro-life sentiment rising—even as attempts to criminalize abortion provoke overwhelming backlash.
This could be a way forward: less logical, but more reasonable; a politics less of first principles, and more of common sense.