I would encourage you to read the article "Obama's Abortion Extremism", by Robert George. Here is an excerpt:
"In an act of breathtaking injustice which the Obama campaign lied about until critics produced documentary proof of what he had done, as an Illinois state senator Obama opposed legislation to protect children who are born alive, either as a result of an abortionist's unsuccessful effort to kill them in the womb, or by the deliberate delivery of the baby prior to viability. This legislation would not have banned any abortions. Indeed, it included a specific provision ensuring that it did not affect abortion laws. (This is one of the points Obama and his campaign lied about until they were caught.) The federal version of the bill passed unanimously in the United States Senate, winning the support of such ardent advocates of legal abortion as John Kerry and Barbara Boxer. But Barack Obama opposed it and worked to defeat it. For him, a child marked for abortion gets no protection-even ordinary medical or comfort care-even if she is born alive and entirely separated from her mother. So Obama has favored protecting what is literally a form of infanticide."
I would also encourage you to read the non-partisan Factcheck.org article on this question. Obama is more extreme than Ted Kennedy, John Kerry, or Barbara Boxer on the Abortion issue. He is now trying to paint himself as a moderate on the issue, who supports banning late term abortions. But he could not even bring himself to banning "abortion" during the fourth trimester... by allowing a baby who survived a botched abortion to die... as happens on a regular basis in abortion clinics in America. He has absolutely no record of actually opposing abortion under any circumstances, when he has had to actually vote on such an issue.
Also, this Roman Catholic Video is worth watching. While we do not share the same faith, we share the same view on this issue: