West Ham's winning run in the Women's Super League was halted by Birmingham as Louise Quinn's second half equaliser saw the sides share a point.
Olli Harder's West Ham side began the game with high intensity but the visitors restricted them to very few sights of goal in the opening 25 minutes.
Five minutes before half-time, Birmingham registered their first effort on goal through Lisa Robertson, whose left-footed effort from long range forced West Ham goalkeeper Mackenzie Arnold into a comfortable save.
The visitors continued to maintain their defensive shape at the start of the second half and Lucy Quinn tried her luck from the edge of the box, but her effort went over the bar.
Three minutes later, Claudia Walker picked up possession in her own half and embarked on a solo run before curling a 20-yard effort over Birmingham goalkeeper Marie Hourihan to give West Ham a deserved lead.
Harder's side could have doubled their lead soon afterwards, with Dagny Brynjarsdottir's cross almost turned in for an own goal before Tameka Yallop's effort at the near post was brilliantly saved by Hourihan.
With 25 minutes remaining, Louise Quinn tapped past Arnold from close range after West Ham failed to clear the danger from Robertson's corner to hand the visitors an equaliser and get their season up and running at the fifth time of asking.
