The Bombay Stock Exchange benchmark Sensex fell by 90 points in opening trade today on sustained selling by foreign funds amid a weak trend in other Asian markets and current month contract expiry in the derivatives segment. The 30-share barometer, which lost over 260 points in the previous two sessions, fell further by 89.96 points to 18,088.37 points today, dragged down by profit-booking in IT and capital goods sectors in the first few minutes of trade. In a similar fashion, the wide-based National Stock Exchange index Nifty fell by 27.25 points to 5,410.10 points.