Lena Petermann scored her fourth goal of the season to put Leicester in front, but a 10-player West Ham fought back in added time to score an equaliser through Honoka Hayashi, resulting in the points being shared with the Hammers.
There was one change to the starting XI that were held to a 2-2 draw with Brighton & Hove Albion a week prior, with the injured CJ Bott being replaced by Courtney Nevin, who filled in on the left flank of a back five, with Janice Cayman moving across to the right.
City dominated a lot of the ball in the opening stages but failed to create any real openings towards the West Ham goal, and after 20 minutes, the visitors started gaining confidence and had the first shot on target, with an effort from outside the box, which forced a good save from Janina Leitzig.
With half an hour gone, City broke into the box as Rantala looked for Cayman, but a diving header from the Belgian wasn't enough to connect with the effort, leaving West Ham relieved to see the ball go out of play.
The final chance of the half fell to Sam Tierney on the edge of the box, but as the midfielder took aim, her low driven attempt was blocked by team-mate Petermann, who was trying to get out of the way of the shot.
The closest either side got to opening the scoring at the start of the second half came when a pass back from Julie Thibaud was mis-controlled by Leitzig, who watched as the ball edged towards the goal, but thankfully hit the post before staying out.
On 69 minutes, the deadlock was broken by the Foxes, who executed a brilliant counter attack which was rounded off with Petermann firing in from close range. Rantala moved the ball forward before picking out Aileen Whelan on the right wing, who supplied the German striker with a low cross to turn goalwards.
Over the final 15 minutes, City looked relatively comfortable but would have to see out another 10 minutes added on to the end of the game. Reduced to 10 after Hawa Cissoko's dismissal, the visitors made the most of their final chance at goal with a deep cross into the box.
Against the run of play, West Ham whipped in a dangerous cross which got the smallest of touches from Hayashi, but was enough to direct the ball goalwards, and Willie Kirk's side could only look on in despair as it trickled across the goal line.
Disappointment at the end of a hard-fought match will not sit easy with Leicester, who now head into the Christmas break off the back of a draw, but another point takes City's tally up to 10 for the season. Scoring goals against every opponent they have faced this term will also be a comfort to the Foxes, who look back on a year of development with hope for their return in January.