Maybe because the pro-choicers killed off their unwanted or inconvenient babies?

According to Gallup:

"Pro-Choice" Americans at Record-Low 41%; Americans now tilt "pro-life" by nine-point margin, 50% to 41%."

The idea that there is a demographic tendency toward pro-life because (a) parents pass on values to children and (b) pro-life parents don't kill their babies was coined the "Roe Effect" by James Taranto. It may exist, but this rapid slide in the popularity of the pro-choice position since the election of Obama suggests that something else is going on.

The relative unpopularity of abortion may be a reason that the Obama administration decided to go after the Catholic Church on "contraception."