“Don’t take Tylenol. Fight like hell not to take it,” he said from the White House on Monday, issuing a warning to pregnant women based on an unproven link between the medication and autism. When a reporter remarked that the American College of Obstetricians and Gynecologists disagreed with his assessment, Mr. Trump said: “You know what? On Monday, Mr. Trump seemed to be in the driver’s seat, celebrating the announcement and going even further than guidance issued by the Food and Drug Administration. The agency did not unequivocally state that pregnant women should not take Tylenol but rather that health care providers should consider the risks and discuss them with their patients.