Child welfare officials conceded to a judge that a newborn's mother, held in foster care as a minor after being removed from a polygamous sect's ranch, is an adult. The woman, who gave birth on April 29, had been held along with more than 400 children taken last month from a ranch run by the Fundamentalist Church of Jesus Christ of Latter-day Saints. She was one of two pregnant sect members who officials had said were minors. The other member, who gave birth on Monday, may also be an adult, state officials said.