Pompey fans once again had to suffer the bitter taste of a late defeat courtesy of Nathan Redmond's 86th minute winner at St. Andrew's.
It looked like the same team that thrashed Peterborough 11 days ago would hold on for a well-earned draw against the division's in-form team but one defensive lapse in the second half proved costly.
The hosts started the game on the front foot and forced Ricardo Rocha into a hashed clearance in the first minute. More long range efforts followed that failed to trouble Stephen Henderson but Pompey then started to grow into the game.
Michael Appleton's side were playing some good football that led to a couple of chances from outside the box, but unfortunately Marko Futacs and Hayden Mullins couldn't find the target with their efforts.
Boaz Myhill was called into action later in the half though, as Kelvin Etuhu burst into the Blues' box and teed up Joel Ward whose shot was destined for the bottom corner until it was saved by the 'keeper.
There were a couple of hairy moments in the half as individual errors from Tal Ben-Haim and Jason Pearce almost gifted Birmingham one-on-one chances but some excellent covering from Rocha prevented that from happening.
Pompey ended the half in the ascendency but could not carry that momentum into the rest of the game as Birmingham penned the visitors in their own half of the pitch.
The Pompey defence dealt with all that Chris Hughton's men could muster, despite Ben-Haim playing a suicidal backpass to Henderson who did well to stop Adam Rooney's point blank effort.
Jordan Mutch then went close as his long range shot struck the post as the pressure mounted.
Pompey's only attack of note came when Benjani set up Erik Huseklepp who would have only had Myhill to beat, but the Zimbabwean had used his hand to control the ball.
Despite the lack of chances, it seemed that Pompey fans would be rewarded for enduring the sub-zero temperatures and the rather pathetic attempts of "banter" from the home side's youth club.
But, not for the first time this season, the late suckerpunch would come as teenager Nathan Redmond was found with plenty of space in the box and he made no mistake of smashing the ball past Henderson.
Appleton brought on Dave Kitson to try and find an equaliser in what little time remained but there was never really any chance of that happening, leaving Pompey fans pondering yet another defeat on the road.
There was nothing too disheartening about the performance in truth and the manager has done well to keep the players focused during a difficult time. We have played worse than that this season and won.
If the team can replicate that level of performance then I'm confident that Pompey will survive relegation when the inevitable ten point penalty is slapped on the club for going into administration, which may be a matter of days now.
The biggest worry is what Andrew Andronikou will do now the emergency loan window has opened. Just how many players will be forced out to pay the bills?
Pompey Player Ratings
Stephen Henderson: 6 - Not much to do as most of Birmingham's efforts were off target.
Tal Ben-Haim: 5 - Two extremely sloppy moments were almost costly.
Jason Pearce: 6 - Generally solid apart from one slip.
Ricardo Rocha: 8 - A rock at the back and got Pompey out of trouble on occasions.
Greg Halford: 6 - Seems to be playing well at left back.
Kelvin Etuhu: 6 - Looks to be a cut above the rest so no surprise to see Birmingham double-up on him.
Liam Lawrence: 6 - Growing into his new role in centre midfield.
Hayden Mullins: 6 - Quietly went about his business.
Joel Ward: 6 - Almost grabbed a goal.
Erik Huseklepp: 5 - Struggled to have any influence in the game. Heavy touch didn't help.
Marko Futacs: 6 - Held the ball up well but Birmingham defence knew how to deal with him.
Substitutes
Jamie Ashdown
Aaron Mokoena
Adam Webster
Benjani (Futacs 75): N/A - Might have created an attack if not for his handball.
Dave Kitson (Etuhu 90): N/A - Desperate switch in search of the equaliser.