The BSE benchmark Sensex fell by almost 200 points in opening trade today. The 30-share Sensex, which had gained 337 points in the previous session, fell by 199.99 points, or 1.17 per cent, to 16,885 in opening trade today.The wide-based National Stock Exchange Nifty Index shed 53 points, or 1.03 per cent, to 5,086.Meanwhile, in the Asia region, Hong Kong's Hang Seng Index was down 0.61 per cent, while Japan's Nikkei shed 0.80 per cent in morning trade today.The Dow Jones Industrial Average in the US closed 0.63 per cent lower yesterday.