Two reasons:
1) To acknowledge a Caesarean as an option would completely refute the bogus "sometimes necessary to save the mother's life" argument that is all this procedure has to stand on. And even though the procedure is the kind of thing we hung Nazis for, the pro-abortion crowd isn't willing to give an inch to pro-lifers, lest the house of cards on which they've built their justifications begin to come down.
2) Fetal tissue = stem cell research = money
2) Fetal tissue = stem cell research = money
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That makes sense. Thanks.