U.S. fixed mortgage rates eased slightly for the third consecutive week to remain at a six-month low, said the Primary Mortgage Market Survey released Thursday by Freddie Mac. The U.S. mortgage giant said the 30-year fixed-rate mortgage ( FRM) declined to 4.20 percent in the week ending Thursday from 4. 21 percent in the previous week. The 15-year FRM, a popular guide for those looking to refinance, edged down to 3.29 percent this week from 3.32 percent in the prior week. "Mortgage rates were little changed amid a week of light economic reports. These lower than expected rates are welcome news with the spring home buying season underway and may even provide those who haven't already refinanced possibly a reason to take another look," said Freddie Mac's chief economist Frank Nothaft in a statement. The five-year Treasury-indexed hybrid adjustable-rate mortgage (ARM) edged down to 3.01 percent this week from last week's 3.05 percent, while the one-year Treasury-indexed ARM kept at 2.43 percent, unchanged from last week. The U.S. housing market has showed signs of slowdown since the second half of last year, as sharp increases in home prices and limited inventories, as well as higher mortgage rates have discouraged many home buyers.