Investing.com - Underlying U.S. inflation rose in February as rents and medical costs maintained their upward trend.The Labor Department said its consumer price index rose 0.3% last month after a similar gain in January. So-called core inflation rose 2.3%, the largest gain since May 2012, after increasing 2.2% in January. The uptick in underlying inflation could keep the Federal Reserve on course to gradually raise interest rates this year.