Check out this article in The Wall Street Journal by John Fund.
"It turns out that while in the Illinois legislature, he voted against a bill that would have defined a fully born baby who survived an abortion as a "person." The concept isn't that controversial even among liberal Democrats. Senator Barbara Boxer of California, the Senate's leading pro-choice champion, urged her fellow Democrats to vote for a federal version of the same concept back in 2001, saying such a provision did not impinge on the rights enshrined in the Roe v. Wade decision legalizing abortion. The Born Alive Infants bill eventually passed the U.S. Senate by 98 to 0.
"But in the Illinois Senate, when Mr. Obama chaired the Health and Human Services Committee, records show a bill consisting of exactly the same language two years later was voted down by six to four. Mr. Obama was one of the legislators opposing it."