Two goals by German striker Shekiera Martinez, the second in injury-time, earned the Hammers a 2-2 draw after they were 2-0 down after 21 minutes.
With four of the season's 22 league games remaining, unbeaten Chelsea, who have been without the injured Sam Kerr all season, are six points clear of second-placed Arsenal, who hammered Crystal Palace 4-0 to push the bottom side closer to relegation.
Arsenal made several changes from the team that reached the Champions League semi-finals in midweek and Caitlin Foord spent the match on the bench. Steph Catley played the full 90 minutes while Kyra Cooney-Cross made a late substitute appearance.
Third-placed Manchester United, who are level on points with Arsenal, eased to a 2-0 win over Everton, while fourth-placed Manchester City, seven points further adrift, beat Dario Vidosic's Brighton & Hove Albion.
Mary Fowler set up City's opener for Kerstin Casparij. Vivianne Miedema appeared to make the game safe in the 90th-minute but Australian Charlize Rule set up a tense finish with an injury-time strike.
At the other end of the 12-team table, Palace remain rooted to the bottom having amassed nine points so far, four fewer than second-from-bottom Aston Villa, who came from behind at Liverpool to secure their first win of 2025.
Leicester City look to be safe in 10th spot after a 1-1 draw at home against Tottenham Hotspur.
with PA
