LOS ANGELES (AFP) - The unmarried teen daughter of Alaska Governor Sarah Palin, whose pregnancy became a US presidential campaign issue in 2008, has reportedly split with her young fianc. Bristol Palin, 18, gave birth to a baby boy in December but has since broken up with the child's father Levi Johnston, 19, People magazine reported. The split happened "a few weeks ago," People said, citing a source close to the couple. "It was a mutual thing," the source said.Bristol Palin in February told Fox News that she planned to marry Johnston after the two finished high school. Asked by Fox News in February for her views on contraception, Bristol Palin said: "I don't want to get into details about that. Everyone should be abstinent but it's not realistic at all." Bristol also said in the interview that she hoped to become an advocate against teen pregnancy.