The Blues found an equaliser in the nick of time after Manchester City were reduced to nine players thanks to some controversial refereeing by Emily Heaslip.
Chelsea's Guro Reiten found the back of the net in the sixth minute of added time after Lionesses Alex Greenwood and Lauren Hemp had been sent off for Manchester City
But Emma Hayes' side looked unconvincing despite their two extra players and Manchester City were unlucky that Chloe Kelly's opener was not enough to earn them the win.
Hayes told Sky Sports after the game: "It's a reminder that just because you have the numerical advantage it doesn't mean you're going to win the game.
"A point away from home is a point gained and a missed opportunity."
Read More in WSL
Chelsea manager Emma Hayes calls for WSL to be expanded to 18 teams
Stunning stats show Arsenal defeat to Liverpool could have huge WSL title ramifications
Meanwhile, West Ham are fresh off the back of a 2-1 comeback win over Charlton Athletic in their first Continental Tyres League Cup group match.
They looked promising in their last WSL match as their high intensity and strong presses throughout the game earned them a 2-0 win over Brighton.
Their quality stretches from end to end as Australian keeper Mackenzie Arnold continues to be as impressive as she was in the World Cup and newly-signed Japanese striker Riko Ueki proved what a threat she is going to be as she netted her first goal against Brighton.
But West Ham have never beaten Chelsea in their fourteen meetings - the best they have been able to salvage is a draw back in 2019.
Most read in Football
Sheepish Rodri backtracks on infamous Scotland comments after boos from Tartan Army
Chelsea wanted stadium with chimneys but it became shops and 'cathedral' plan was ditched
England vs Australia build-up, Spurs claim Premier League awards double
Grealish only ever dreamed about Villa, but won the Treble and now wants England glory
Victory for the Hammers would be monumental for their season and could do some serious damage to Chelsea's title campaign.
Chelsea: slow and steady wins the race?
It has been a familiarly slow start to the WSL for the defending champions.
Their opening 2-1 win over Tottenham was anything but pretty and they were lucky not to have their efforts cancelled out by Martha Thomas' late efforts on goal.
Their 1-1 draw with Manchester City was even more fortunate after they were gifted a nine-player opposition for almost an hour of the game.
But as history has taught us, this is the Chelsea way: a rocky result or two in their opening few games has become just the precursor to another runaway WSL victory.
Last season's opening defeat to Liverpool for example, was one of just two defeats they suffered - incidentally, the other loss was in their away fixture to Manchester City.
Not to mention that their lineup has been boosted by the returns of Chelsea's all-time top scorer Fran Kirby, as well as another striker who is only six goals off her record - Sam Kerr.
The bottom line remains that Chelsea have not lost two league games in a row for more than five years: this team knows how to deal with setbacks.
The most red-carded player in WSL history - but for how long?
Chelsea are no stranger to seeing red cards handed out after seeing Greenwood and Hemp sent off for Manchester City.
But when they face West Ham, they will be facing a defender who holds the title of the most red-carded player in the history of the WSL.
Hammers defender Hawa Cissoko has picked up just three red cards in the WSL - by comparison, the most red-carded player in the Premier League picked up eight red cards.
That such a low tally constitutes the record is a reflection of how uncommon red cards are in the WSL - until now.
If recent WSL officiating is anything to go by, Cissoko may not hold her record for very long.
The decision to send Greenwood off against Chelsea is being widely criticised after it was revealed that she took 26 seconds to take the free-kick which ultimately earned her a booking for time-wasting.
Ian Wright took to X, formerly known as Twitter, where he wrote: "Embarrassing. They keep telling us about laws of the game but where is common sense! Why would she be wasting time???"
Lioness Beth Mead also wrote: "Awful decision, never time wasting."
Manchester City alone have now picked up three red cards in their first two games - there were only eight red cards shown to all teams during the entire WSL season last year.
Players like Cissoko - whose most infamous red card was given for an altercation she had with Aston Villa's Sarah Mayling - could now face more stringent punishments for offences which might previously have been allowed.
But Cissoko insisted she would not change her approach and she told The Athletic: "If I want to change the picture, I have to change my game, and if I change the way I play, I won't be good."
She said: "I'm fast, I'm strong and I'm powerful. If I stop being me, West Ham are going to rip up my contract and I will be playing Sunday league."
After Manchester City's two red cards influenced a game which might ultimately be crucial in deciding the eventual champions, it remains to be seen just how pivotal red cards could be in determining this year's WSL champions.
West Ham: the mid-table masters in need of stable management
Since gaining entry to the WSL in 2018, West Ham have been a largely unremarkable side.
They have always finished somewhere between sixth and ninth in the WSL table, never having performed particularly well or particularly terribly.
The closest they have ever come to glory was the 2019 FA Cup final when they were defeated by Manchester City.
What West Ham have lacked during their time in the WSL is consistency of management.
Current Liverpool boss Matt Beard who steered them through their first few seasons, before he was replaced in 2020 by New Zealander Olli Harder.
But the 2022 season saw his replacement Paul Konchesky take the reins.
As a former West Ham, Liverpool and Leicester City player and a lifelong Hammers fan, the club had high hopes for Konchesky.
He did not entirely disappoint, leading West Ham to a respectable semi-final finish in the Continental Tyres League Cup.
But ultimately, West Ham only won six out of their 22 WSL games last season - and Konchesky went the way of his predecessors.
Enter Rehanne Skinner - the former Tottenham manager who was sacked in March 2023 following a run of nine straight league defeats for the club.
West Ham's early performances give indications they could be on the rise under Skinner.
But perhaps more important than Skinner's performance this season with West Ham will be the platform that she builds for the future.
Emma Hayes has been manager at Chelsea since 2012; Arsenal have had Jonas Eidevall since 2021 and know they will have him for at least three more; Manchester City's Gareth Taylor is beginning his third season with the club after spending his entire coaching career with the youth team.
West Ham's inability to move into the top half of the WSL table is linked to their inability to find a manager who will commit to the club in the long-term.
With players like Arnold, Ueki and experienced right-back Riza Shimizu in the fold, the Hammers have all the tools.
Now they need a boss who can plan for their development two or three seasons ahead and know they will still be there to direct those changes themselves.
West Ham will likely finish this season in the mid-table as they have always done.
But the true measure of their progress will come next season, and the ones after when - hopefully still under Skinner - they could start moving up the table.
Read More on talkSPORT
Chisora says Fury vs Ngannou will be a 'walkover' after seeing 'The Predator' training
Tim Ream praised for going 'above and beyond' during Chris Basham's horror leg break
And if Skinner is to take West Ham to new heights - a first ever win over defending champions would not be a bad place to start.
You can tune into live commentary with Joe Shennan and Courtney Sweetman-Kirk on talkSPORT 2 as Chelsea host West Ham from 5:30pm on Saturday 14 October.