Docked nine points during the international break, Birmingham returned to the field and endured another painful experience.
Garry Monk's side led twice at West Brom but ended up losing when Jake Livermore struck a rocket of a shot to confirm fears a relegation fight cannot be ruled out just yet.
Punished for spending breaches, Birmingham went from having an outside hope of the play-offs to trying to stay above the dotted line when the EFL finally delivered their punishment last week.
So this loss, a fifth in a row, will prompt concern. Monk's team are five points above Rotherham in 22nd place having played a game more, with Leeds and Sheffield United up next.
Birmingham could also have done without two fans trying to get on the pitch in celebration of their side's second goal, three weeks on from Paul Mitchell being jailed for assaulting Jack Grealish.
West Brom were not at their best but ground out a third win in a row under caretaker manager James Shan, who is in pole position to keep the job for the remainder of the season and into an expected play-off campaign.
West Brom have not announced any decision, having previously paused on a move for Slavisa Jokanovic, but the board are happy to maintain the status quo with results so positive.
'I'm employed by the football club and I'll do whatever they ask me to do,' Shan said. 'I'm happy to keep going game by game. The lads are comfortable with myself.'
Monk said the result was 'very tough' on his players tonight. 'We put a performance on that warranted more,' he added. 'We have adversity all year long. We trust in ourselves.'
This being a Friday night under the lights between local rivals the atmosphere sizzled from the off. And it did not take long for those noisy travelling fans to have something to cheer.
Seven minutes were on the clock when Gary Gardner escaped attentions of West Brom's defenders at Connor Mahoney's corner to head in unchallenged from six yards.
Wild celebrations in the away section saw two blue smoke bombs thrown onto the pitch, not exactly helping goalkeeper Lee Camp's vision or Birmingham's bruised reputation.
Those same fans gave their verdict on their club's nine-point deduction. 'F*** the EFL,' they sang.
A minute after the restart though, West Brom drew level. Chris Brunt curled over a perfect free-kick and Dwight Gayle glanced on to defeat Camp for his 17th goal of the season.
Birmingham retook the lead just before the hour. Mahoney delivered another deep corner and Lukas Jutkiewicz beat Jay Rodriguez in the air to nod down and in.
Scoring in front of the travelling fans encouraged two men to leap the hoardings to join the players.
There was none of the malicious intent that fuelled Grealish's assailant but the West Brom stewards were understandably on guard and forcibly led both Birmingham supporters away.
So they missed West Brom's comeback, which began with an equaliser again six minutes later. Mahoney undid his two assists by sliding in foolishly on Conor Townsend.
The foul began outside the box but continued inside and referee David Webb was right to point to the spot. Rodriguez converted confidently, sending Camp the wrong way.
And West Brom won it 16 minutes from time when Livermore unleashed a fearsome half-volley. Harlee Dean and David Davis failed to properly clear Gayle's cross and Livermore's shot tore through the crowd.