CHARLESTON, W.Va.-- Police in Boone County are reviewing hundreds of pages of medical records regarding a mother accused of trying to suffocate her infant son at least 15 times at home and at hospitals in Pennsylvania and West Virginia.A judge in Allegheny County, Pa., found probable cause on Wednesday to move the case against Rachel Nelson, 22, of Costa, ahead toward trial.Nelson has been held under evaluation at the Western Psychiatric Institute and Clinic in Pittsburgh since last month. Police say Nelson tried to suffocate her 4-month-old son at the University of Pittsburgh Medical Center's Children's Hospital on Oct. 20.She was charged in October with felony aggravated assault, endangering the welfare of a child and reckless endangerment of another person. She is being held in Allegheny County Jail in lieu of a $100,000 bail.Boone County Sheriff Rodney Miller said detectives are still poring through the boy's medical records in West Virginia to determine if charges would be pressed against Nelson here."I sent one of our deputies up to Pittsburgh when she was released from the hospital to interview her," Miller said. "Right now we are working with the prosecutor to see what direction we need to take."Police said they are looking into at least 15 instances in which Nelson is accused of nearly suffocating the infant and then resuscitating him. She would allegedly take him to area hospitals for treatment, where doctors failed to pinpoint the cause of the child's affliction.The boy was transported from CAMC Women and Children's Hospital to the UPMC Children's Hospital on Oct. 18 for treatment of "intermittent respiratory distress," Pittsburgh Police Lt. Kevin Kraus said.Hospital medical staff found the boy limp with abnormal breathing in the intensive care unit two days later, Kraus said. Hospital security called police after reviewing surveillance footage showing Nelson allegedly holding the boy moments before.Police detectives interviewed UPMC Children's Hospital medical staff, Nelson and her husband, Shawn. Detectives said Nelson told them she nearly suffocated her son several times from August through October, including twice at UPMC Children's Hospital, Krauss said.Nelson allegedly told detectives she "blacked out" during the incidents. Kraus said she would hold the boy against her chest and tighten her grip when he struggled for air."He was just shy of death and she would then revive him," Kraus said.Police contacted Child Protective Services in Pennsylvania and West Virginia, which seized custody of the infant. Kraus said Shawn Nelson, 43, the infant's father, cooperated with the investigation and would not be charged. The child remains under evaluation at the hospital. Miller said police have had no prior run-ins with Nelson.Reach Travis Crum at firstname.lastname@example.org or 304-348-5163.