Sunderland were beaten for only the second time this season, going down to a late goal at home to Aston Villa.
The league's last unbeaten record fell as Barnet took the points with a late winner at Cardiff City.
Nottingham Forest made it three wins on the trot with a 4-2 victory away to third-placed Coventry City
Reading won 3-1 at Watford in the basement battle, a Nicola Watts brace sending her clear at the top of the goalscoring chart.
Sunderland 1-2 Aston Villa
The league leaders were trailing at the interval to Ini Umotong's 23rd-minute effort for Villa, hooked home from an inswinging corner.
Villa soaked up the pressure until the 83rd minute when Kelly McDougall found Beth Mead, who found the roof of the net from 25 yards.
However, hesitation between the Black Cats' keeper and a defender saw Emma Follis nip in to steal a late winner.
Cardiff City 1-2 Barnet
Cardiff broke the deadlock five minutes before the break when Natasha Harding took advantage of a miscued clearance to finish smartly into the bottom corner.
Cheryl Williams pulled the Bees level early in the second half, with a curling effort from the edge of the area.
With just two minutes left, good work by Stacey Sowden enabled Renata Inniss to give Barnet the points, with her first goal in only her second appearance.
Coventry City 2-4 Nottingham Forest
Sophie Bradley struck first for Forest on 25 minutes, then Andi Bell outpaced Natalie Wilcox and sidefooted past Sue Wood for the second before half-time.
Suzanne Davies headed home unchallenged from a free-kick to make it 3-0, before the Sky Blues pulled one back when Jade Formaston curled a shot into the top corner from 23 yards.
Bell got the fourth in the 90th minute when City failed to clear their lines, Courtney Sweetman-Kirk replying instantly.
Watford 1-3 Reading
In a fast-paced first half the Hornets took a ninth-minute lead when a mix-up allowed Lois Roche to sidefoot home from the edge of the box.
Nicola Watts was put through by Stacey Donnelly to level after 28 minutes and four minutes into the second half the same combination doubled the Royals' tally.
In injury time, Becky Jane beat two players to complete the scoring via the far post.