I doubt he’s every had any strong feelings on the issue, but looks like this is the position he intends to stick with now.
Romney has always had extraordinarily strong and passionate views on abortion, he has been very effective and warm when explaining the importance of keeping abortion legal, he tells how the death of a close family friend showed what can happen when abortion is outlawed.
Being pro-abortion as a Senate candidate is what he most admires about his “courageous” mother.