The search for what authorities feared was a desperate mother and newborn in grave medical danger was called off yesterday after police located the woman whose placenta was found in a Wellesley College pond. Mom and baby are both healthy, police said. “No one was ever at any time in any danger at all. After completing the investigation, we are sure of that,” said Wellesley police spokeswoman officer Marie Cleary. “The baby was never in any kind of jeopardy.” The Wellesley mom gave birth “a number of months” ago and she and her husband preserved the placenta on their own,...