PHILADELPHIA (AP) — An unlicensed doctor pleaded guilty to third-degree murder in the deaths of two babies who were born alive and then killed with scissors at a filthy Philadelphia abortion clinic.Steven Massof, of Pittsburgh, pleaded guilty to two counts of third-degree murder, murder conspiracy and other charges on Thursday.The 49-year-old Massof is the fourth of 10 defendants to plead guilty in the case.Seventy-year-old Dr. Kermit Gosnell is charged with killing seven babies and a woman who died after a botched abortion at the clinic he owned.Massof's two murder counts could bring a life term, but he'll likely get a reduced sentence for his plea and potential cooperation.He remains in custody. He graduated from a foreign medical school, but was not licensed to practice medicine.