Striker Leah Galton scored two quick-fire first-half goals as Manchester United hammered Birmingham City 5-0 to rise to third in the WSL table.
After spending the winter break in last place, Birmingham got off to a flying start in the WSL.
Frida Maanum scored two headed goals in three minutes as Arsenal hammered Leicester City 4-0 to go four points clear at the top of the WSL.
Kim Little scored twice as Arsenal thrashed West Ham United 4-0 on Sunday to make it six wins from six FA Women's Super League games.
Katie McCabe scored one goal and made another as leaders Arsenal remained top of the Women's Super League table thanks to a 3-0 win over Everton.
Newcomers Leicester City lost 3-1 to Manchester United in their first FA Women's Super League home game.
Manchester City kicked off their Women's Super League campaign with a 4-0 win at Everton, while Tottenham enjoyed victory over Birmingham City.
Chelsea will begin their Women's Super League title (WSL) defence with a trip to London rivals Arsenal.
USWNT and Manchester City midfielder Sam Mewis marked her comeback from injury on Sunday with a brace as her side beat Birmingham City 4-0.