The Sky Bet Championship leaders saw their run of games without a win stretch to three as Birmingham gave the Magpies a real scare with their determined attacking play and were the better side for several spells of the game.
The most worrying aspect of the game for Newcastle was their high scoring attack have suddenly lost their lethal finishing power as they head into the final stage of the season.
Newcastle staged a late surge in this game but Birmingham steadfastly refused to surrender as goalkeeper Tomasz Kuszczak took the honours with a string of fine saves.
Although Birmingham went into the game with a record of only nine points from 13 games this year they played with a great deal of confidence and operated effectively on the counter.
Newcastle, who surprisingly left Dwight Gayle and Jonjo Shelvey on the bench, appeared to be a little over anxious despite applying a lot of pressure.
United, unbeaten in their previous nine visits to St. Andrew's, failed to capitalise upon some good work by Matt Ritchie. Emilio Nsue was given plenty of scope down Birmingham's right flank as he proved with their first chance.
Despite monopolising most of the attacking play Newcastle struggled to break down a determined Birmingham rearguard in which veteran Paul Robinson and Ryan Shotton proved efficient stumbling blocks to the United attack.
It was Birmingham who should have gone ahead in the 26th minute. David Davis found Lukas Jutkiewicz at the far post but the striker screwed his shot wide from close range.
The incident appeared to put the Magpies out of their stride as Birmingham began to play with more confidence.
Strangely Newcastle's strike force struggled to make an impact with Daryl Murphy completely shut out in the first period.
Ritchie, who was Newcastle's most dangerous player, managed to get the ball into the net five minutes before the break following a melee but the effort was disallowed by the assistant referee for offside.
Battling Birmingham were kept in the game by a brilliant save by Kuszczak eight minutes into the second half when he was forced to dive low to his left to keep out a close range header from Murphy.
But Birmingham continued to play with growing confidence as they belied their indifferent form this year. The persistent Jutkiewicz was always a potential danger as he demonstrated with a low angled shot.
In the 62nd minute Newcastle finally drafted in Gayle in an attempt to inject more finishing power and it took a desperate near post save by Kuszczak to prevent the striker from opening his account.
As Newcastle stepped up a gear Shelvey was introduced but he could not inspire a late win as Birmingham held on for a precious point.