Actually, it seems to me that a lot of abortions probably happen because of the stigma. Ironically, the lessening of the stigma may reduce the number of abortions.
It isn’t the stigma. There is no stigma about having unmarried sex, especially as a teen, these days.
It is selfishness. “I don’t want to have a baby right now”, “I don’t want to give up my baby to someone else”, “I don’t like the guy THAT much”...