West Ham could have been 2-0 up at one point during the first half of the contest at Meadow Park against an unbeaten Arsenal side.
However, a questionable refereeing decision from a corner which disallowed Dagný Brynjarsdóttir's header and went in favour of Kim Little meant that the Gunners, rather fortuitously, only had a one-goal deficit to make up, which they did with some ease as the contest progressed.
Goals from Jordan Nobbs, Stina Blackstenius and Frida Maanum were enough to sink the Hammers in the end and continue the north Londoners' 13-game winning streak in domestic competitions.
