After gaining in the previous two sessions, the BSE Benchmark Sensex lost 13 points to 19,292.43 a short while ago. Earlier the Sensex fell by over 31 points in the opening trade today as investors preferred to adopt a cautious approach ahead of the vote on FDI inParliament and trimmed their positions.The NIFTY at the National Stock Exchange was trading 5 points in red at 5,866.