Memes which dominate the national conversation trump science. And the meme that the fetus feels pain at about 20 months has become a powerful tool for the pro-life movement. As Olga Khazan points on in THE ATLANTIC, science has yet hasn't agreed on at what stage of gestation the fetus will experience pain during an abortion. Here is that article.
Even in our bare-knuckled capitalist nation, we back off from inflicting pain. That's how the supposedly painless death through lethal injection came about. We don't even want to allow those suspected of heinous crimes to miss their dinner. Hunger hurts, after all.
Shrewd conservatives can piggyback on the pain contention to regain influence for the 2014 elections. This has been a smart move for the right-to-life advocates.