Women's Super League leaders Chelsea had their title hopes jolted in a 1-0 defeat at second-bottom Notts County.
A Jess Clarke goal gave County only their second win of the season and left Birmingham with the chance to go top with a win against Liverpool on Sunday.
Arsenal gave new manager Pedro Martinez Losa a dream debut with a Kelly Smith-inspired 4-3 win at Bristol Academy.
Smith entered the fray as substitute with the Gunners 2-0 down but hit a hat-trick to turn the game around.
|Women's Super League|
Notts County 1-0 Chelsea
After an evenly contested opening, the game at Meadow Lane burst into life in the 39th minute when County goalkeeper Carly Telford saved Yuki Ogimi's header.
From Telford's clearance the home side went in front almost immediately, the Magpies winning a free-kick that midfielder Katie Hoyle delivered for striker Clarke to head home.
Another Hoyle set-piece, this one a 53rd-minute corner, almost led to a second goal but Danielle Brogan's header was cleared off the line.
In the final half-hour Chelsea, desperate for points to keep themselves clear at the top of the table, pressed hard.
Substitute Rachel Williams might have equalised in the 75th minute but, after beating Telford to the ball, her shot was blocked by defender Amy Turner.
Katie Chapman and Ji So-yun then sent good efforts narrowly over the bar but County held on to boost their chances of avoiding relegation.
Victory lifted the Magpies seven points clear of bottom club Everton, who have four games remaining.
Bristol Academy 3-4 Arsenal
It was Smith to the rescue after Bristol had looked set for victory at half-time.
A second-minute Angharad James corner led to Jasmine Matthews forcing in the opener while Nikki Watts doubled the advantage with a 35th-minute penalty following a foul on Natalia by Alex Scott.
Smith was sent on shortly before the break and four minutes after the restart she reduced the arrears with an 18-yard drive, while moments later Danielle Carter's downward header set up Smith to level from close range.
The visitors edged in front when Scott raced on to a fine pass by Jordan Nobbs to shoot home before Smith completed a 16-minute hat-trick from the penalty spot following a foul on Carter by Jemma Rose.
Natalia gave Bristol hope of collecting at least a point when she pulled a goal back in the 73rd minute but Arsenal saw the game out to move within two points of third-placed Liverpool.