Many opponents of abortion today are motivated by

The idea that a fetus/embryo is still a human. You wouldn't kill a baby once it was born, neither would you kill a developing baby, regardless of the fact it cannot think or really feel yet. The religious motivation is that you shouldn't try to control death and life, if a baby is developing, then God allowed it to for a reason. The divine and predestined purpose concept.

He droped it over the bridge into the river