* Declines in big tech-related firms pressure Nasdaq, S&P 500 * Walmart slides as tepid outlook overshadows upbeat Q4 sales * Facebook shares slip on news blackout move in Australia * Indexes down: Dow 0.28%, S&P 0.41%, Nasdaq 0.72% (Adds dateline, byline, mid-afternoon prices) NEW YORK, Feb 18 (Reuters) - Wall Street stocks fell on Thursday as investors shifted out of big technology names, while an unexpected rise in weekly U.S. jobless claims pointed to a fragile recovery in the labor market. Shares of Apple Inc, Microsoft Corp, Tesla Inc and Alphabet Inc were down between 0.5% and 1.2%, weighing on both the benchmark S&P 500 and the tech-heavy Nasdaq. Facebook Inc shares dropped 1.6% as Wall Street assessed the wider ramifications of its move to block all news content in Australia. Strong earnings, progress in the vaccination rollout and hopes of a $1.9 trillion federal stimulus package helped U.S. stock indexes again hit record highs at the start of the week. But the months-long rally suggests stocks now have high valuations, said Jason Pride, chief investment officer for private wealth at Glenmede in Philadelphia. “We are still in the cautiously bullish environment for the market on the whole,” Pride said, citing two reasons. “We’re going to get a vaccine-induced economic recovery, that’s No. 1. The flip side of that story is the markets have largely priced that in and driven themselves to over-valued territory. Markets are going to struggle with that,” he said. Concerns over a rising inflation outlook have pushed investors to book profits on stocks with high valuations in the S&P 500 technology and communications services sectors, which have underpinned a 76% rise in the S&P 500 since its March 2020 lows. Peter Essele, head of portfolio management at Commonwealth Financial Network in Boston, said there was a lot of irrational exuberance built into stock prices heading into this year. “We started to enter an environment where risk actually became a factor once again and notably inflationary risk,” he said. “Now it’s a question of whether the fundamentals are going to match the level of prices that currently exist.” ADVERTISEMENT A Labor Department report showed initial claims for state unemployment benefits rose to 861,000 last week from 848,000 the prior week, partly due to potential claims related to the temporary closure of automobile plants due to a global semiconductor chip shortage. Of the 11 major S&P 500 sectors, utilities was the only one definitely in positive territory. Consumer staples and discretionary shares traded slightly higher. Walmart Inc slid 5.8% after the world’s largest retailer missed quarterly profit estimates and predicted fiscal 2022 net sales to rise in the low single digits. By 2:53PM ET, the Dow Jones Industrial Average fell 112.76 points, or 0.36%, to 31,500.26, the S&P 500 lost 18.55 points, or 0.47%, to 3,912.78 and the Nasdaq Composite dropped 110.25 points, or 0.79%, to 13,855.25. Marriott International Inc rose 0.6% after reporting a quarterly loss as the hotel chain’s bookings declined due to pandemic-induced travel restrictions. Declining issues outnumbered advancing ones on the NYSE by a 2.32-to-1 ratio; on Nasdaq, a 2.28-to-1 ratio favored decliners. The S&P 500 posted 14 new 52-week highs and no new lows; the Nasdaq Composite recorded 88 new highs and 16 new lows.