Goals before the break from Jade Pennock, who continued her good form, and a stunning strike from Veatriki Sarri put the Blades in control before an equally good strike from Katie Rood made for a tight last half an hour.
The Blades started on the front foot and it was Maddy Cusack who went closest when she fired in a free-kick which was held by Faye Baker.
Just minutes later United did take the lead as Pennock continued her superb form. Cusack was the provider and after steadying herself in front of goal, Pennock slotted home past Baker to make it 1-0.
Carla Ward’s side maintained their momentum throughout a dominant first half and went close when Katie Wilkinson saw a header cleared off the line.
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It was 2-0 before the break when Sarri let fly from 30 yards and the ball nestled in the top corner to double the lead.
The second half was a tighter affair with less clear-cut chances but the visitors were still dominating the ball, though it was Lewes who halved the deficit when Rood hit a stunner across Becky Flaherty and into the far corner.
There was a return to action for Kasia Lipka with ten minutes to go as the Blades looked to hold onto a vital three points, which they did without Flaherty being overly troubled in the final stages of the game.
Lewes (5-3-2): Faye Baker; Sophie O’Rourke, Rhian Cleverly, Caitlin Hayes, Danielle Lane, Ella Powell; Ellie Noble, Ava Rowbotham, Emily Donovan; Katie Rood, Jess King
Substitutes: Charley Boswell for King 46, Filippa Savva for Rowbotham 46, Emma Jones for Noble 73
Substitutes not used: Sam Quayle, Annie Timoney, Laura Hartley, Amy Taylor
Sheffield United (4-3-3): Becky Flaherty; Sophie Barker, Leandra Little, Naomi Hartley, Veatriki Sarri; Sam Tierney, Aimee Palmer, Maddy Cusack; Jade Pennock, Katie Wilkinson, Olivia Fergusson
Substitutes: Alethea Paul for Wilkinson 66, Kasia Lipka for Palmer 80, Chloe Dixon for Sarri 80
Substitutes not used: Emily Batty, Keri Matthews
Referee: Steven Hughes
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