It was, in part, down to a fine display from Blues goalkeeper Tomasz Kuszczak, who kept out Daryl Murphy's goalbound header after the break and also denied Matt Ritchie as Rafa Benitez's men - who saw a Ritchie strike chalked off for offside before the break - looked for a second half winner at St. Andrew's.
But it wasn't to be, and despite the introduction of Dwight Gayle, Jonjo Shelvey and Christian Atsu from the substitutes' bench, United couldn't quite find the goal that would have earned all three points and the game finished goalless.
An open first quarter of an hour brought few real chances as the teams reacquainted themselves with each other for the fourth time this season. Yoan Gouffran, preferred to Atsu on the left wing, turned Paul Dummett's cross goalwards, but it was blocked before it could trouble Kuszczak.
Gianfranco Zola's side then threatened through full back Emilio Nsue, who burst onto Lukas Jutkiewicz's cross at the back post. His first time effort, though, was blocked, and Gouffran was able to get himself in the way of Craig Gardner's follow-up.
A beautifully-weighted pass from Gardner then gave Jutkiewicz a sight of goal, but the former Middlesbrough man could only find the sidenetting. A long throw from Jonathan Grounds was flicked on at the front post by Ryan Shotton, and Karl Darlow had to be alert to parry it away from goal as the Blues continued to apply pressure.
Before the break, United rallied, with Grant Hanley's long ball finding Ritchie. His first touch took him round goalkeeper Kuszczak, but Shotton got back just in time to clear.
And Ritchie had the ball in the net barely a minute later. Ayoze Perez slid in to connect with Vurnon Anita's cross and when Kuszczak parried it, Ritchie bundled in from close range after a scramble in the box. But Akil Howson, the assistant referee on that side, raised his flag for offside, disallowing the goal that would have sent the Magpies in leading at the break.
Murphy burst into the box after the break and forced a save from Kuszczak and after Ritchie's shot was deflected wide, the Polish stopper produced a magnificent one-handed save to prevent Murphy's header from creeping in the far corner.
Leading goalscorer Gayle was introduced in place of Murphy with just under half an hour remaining, and he created an opening just minutes after entering the fray, turning his man and crossing before Jack Colback's shot from the edge of the box was charged down.
Former Sunderland man Gardner tried his luck at the other end, but the second period was dominated by the visitors. Gayle won a free kick on the edge of the box, drawing Shotton into a foul, but Ritchie's effort hit the wall and Gayle's follow-up looped off a Birmingham body and safely into Kuszczak's grasp.
Substitute Shelvey fed Ritchie with ten minutes left, and his right-footed strike was once again tipped away by Kuszczak.
And though Atsu was thrown on late on as Benitez sought a winner, it wasn't forthcoming as the contest ended in stalemate.
