Arsenal had not lost a single time.
Birmingham had not won a single time.
There was only one outcome in the Super League match on Sunday - but that did not happen.
Birmingham started shocked with a goal after three minutes.
Lucy Quinn hit an elegant cross to Libby Smith who put 1-0.
2-0 came just before the break through Greek Veatriki Sarri.
Arsenal had a great opportunity to reduce when Kim Little scored an open goal, but this time Birmingham's Gemma Lawley blocked.
Arsenal still lead the Super League ahead of Chelsea and Tottenham.
With the victory, Birmingham rose from the second place, past Leicester.
A team leaves the English top league.