Goals from Keira Walsh, Tessa Wullaert and Lee Geum-min sealed the three points that move City to the top of the WSL table.
It’s now seven wins from seven in all competitions for Nick Cushing’s side this season.
City took control of the game immediately, moving the ball quickly and dominating possession. Birmingham, who have made a poor start to the campaign, looked somewhat overwhelmed by City’s high-intensity game.
Aoife Mannion and Janine Beckie were particularly threatening down City’s right, and it was the Canadian who had the first real chance, her low drive whistling just past Hannah Hampton’s far post.
Beckie had another chance moments later. A superb through-ball from Keira Walsh split the Birmingham defence in two and put Beckie in on goal, but her effort was palmed away by Hampton.
From the resulting corner, City were ahead. The ball fell to Walsh 25 yards from goal, and her shot deflected past a helpless Hampton. A deserved lead for City, who had been far more ambitious in the opening exchanges.
Our front three were fluid, each comfortable in any position across the front line, and with Mannion and Megan Campbell looking to get forward and supplement attacks at every opportunity, it was a free-flowing, quality football - a continuation the vibrant, attacking style we’ve seen from Cushing’s side so far this season.
Birmingham did well to get to half-time just a goal behind.
City’s aggressive start to the second-half almost paid off when Luaren Hemp’s effort hit the post - but seconds later our lead was doubled, Tessa Wullaert tapping home with an impudent first-time finish after good work from Beckie.
With City in cruise control, Wullaert almost grabbed another – but her left-footed drive came back off the upright and Birmingham were able to clear their lines.
Substitute Lee Geum-min added a third late on with an emphatic close-range finish, and Hemp was inches away from making it 4-0 as she stretched to convert a cross from the right.
Four wins from four is a fine start to the WSL season – but with the standard in the division improving rapidly, Cushing will be taking nothing for granted.
Player of the Match
Keira Walsh. Opened the scoring and was superb throughout. Few players at this level can control a game like her.
A special mention, too, for Jill Scott, whose constant running and pressing created a platform on which our forwards could excel - and Janine Beckie, who ran Birmingham ragged during periods of the game and will be an asset for City this season.
What it means
The result sees City leapfrog Arsenal and move top of the WSL table. The Gunners face Chelsea tomorrow afternoon and a win would see them go back into first place on goal difference.
City have won all four WSL matches thus far and are yet to concede a goal.
City are next in action in the UEFA Women's Champions League against Atletico Madrid at the Academy Stadium on Wednesday 16 October (7pm). Tickets for all home games are on sale online and at the Etihad Stadium Ticket Office.