United returned to winning ways, to stay in the hunt for second sport, as a Nat Shaw hat-trick helped the Blades comfortable see off their opponents for a third time this season.
Georgia Stevens opened the scoring, smashing in a cross from the right, following a fine run by Evie Robinson and Shaw added a second, firing home into the top corner after twisting and turning away from two defenders.
Shaw then turned provider for Hollie Barker to add a third, before getting her second of the game shortly before the break with a brilliant finish.
The second-half was a more scrappy affair and Birmingham reduced the deficit, scoring from a free-kick with 10 minutes remaining.
But the Blades finished the game as they'd started it, with Shaw completing her hat-trick, to take her tally for the season to 23.
United remain firmly in the hunt for second spot in the table, despite Burton beating Rotherham and face TNS in their penultimate game of the season on the 13th May.
Blades: Houldsworth, Robinson, Spurr, Marshall, Barker, Bell, Hickerman, Hartley, Stevens, Shaw, Marsden.
Subs: Neary, Brown, Kenyon, Froggatt.