David Parker's Blues side took the lead after 48 minutes at Borehamwood, when Rachel Williams (pictured) converted from the penalty spot.
But the visitors' advantage lasted just three minutes before Gemma Davison fired home from the edge of the box for the hosts to level the scores.
With the game seemingly heading towards a draw, Ellen White headed in an 88th minute winner for the reigning Women's Super League champions.
A full match report will appear on birminghamcityladiesfc.co.uk
: Laura Bassett, Emily Westwood, Josanne Potter, Melissa Lawley, Kerys Harrop, Isobel Christiansen, Rachel Williams (Kirsty Linnett, 77), Jade Moore, Rachel Unitt, Mary Earps, Chelsea Weston.
Subs not used: Emily Simpkins, Katie Wilkinson, Coral-Jade Haines, Marie Hourihan, Marie Ballard, Cristina Torkilsen.