A Matt Ritchie brace – the first a penalty – and a fine individual effort from Yoan Gouffran made sure of the Magpies’ progression, setting up a meeting with League One outfit Oxford United in the last 32.
Birmingham had created something of a nervy finale thanks to David Cotterill’s strike, but Ritchie’s second – deep into added time – allayed any fears of an additional 30 minutes.
Youngsters Dan Barlaser, Yasin Ben El-Mhanni and Stuart Findlay were all handed their debuts against Gianfranco Zola’s side, with Jonjo Shelvey returning to action after a five-game absence.
And Shelvey’s impact was almost instantaneous. After an uneventful opening ten minutes, the midfielder brought the tie to life with a defence-splitting pass which set Gouffran racing in on goal.
However, the Frenchman was felled by the Blues’ Adam Legzdins, allowing Ritchie the opportunity to step up and power the ball home from 12 yards.
The Birmingham stopper was then forced into a fine save to deny Shelvey himself, palming a rasping 30-yard strike wide before defender Ryan Shotton hacked the ball clear.
At the other end, only a vital block from DeAndre Yedlin prevented David Davis from converting Che Adams’ cross, before ex-Swansea City winger Cotterill curled high and wide from 20 yards.
Just shy of the half-hour mark, young defender Findlay set Achraf Lazaar away down the left, and the Moroccan’s square was turned just wide by Gouffran.
But, five minutes later, the Frenchman made no mistake after being presented with another chance – Shelvey again the architect.
He gathered the midfielder’s dinked set-piece with his back to goal, flicked the ball into the air, and superbly found the far corner on the volley.
The Magpies continued to make all of the running, and just before the break, Ritchie clipped the far post from just inside the area after getting the better of Birmingham’s Jonathan Grounds.
Though they were slow to come out of the traps, Birmingham did finally improve as the second half progressed. Just after the hour-mark, Davis did well to get away from Shelvey and Cheick Tiote 20 yards out, but failed to keep a left-footed strike on target.
However, the Blues were almost further behind just seconds later, as Lazaar drew a fine save from Legzdins after meeting Gouffran’s driven cross six yards out.
It was to prove an important stop, as the visitors halved the deficit with their next attack of note.
Grounds’ cross from the left was nodded down by Maikel Kieftenbeld, and Cotterill was afforded the time to find the net from 12 yards.
Their tails up, Birmingham soon went close again. Substitute Lukas Jutkiewicz rose to meet Cotterill’s set-piece from the left, but his header narrowly cleared the crossbar.
Shelvey then looked to put the outcome beyond doubt once and for all, but couldn’t quite keep a vicious right-footed effort on target.
It was to prove academic in the end, though, as United made sure of the win in the dying embers.
Shelvey again provided the assist, squaring for Ritchie to convert from barely two yards out with just seconds left on the clock.
Newcastle United: Matz Sels, DeAndre Yedlin (Isaac Hayden 75), Grant Hanley, Stuart Findlay, Achraf Lazaar, Cheick Tiote (Jack Colback, 82), Jonjo Shelvey, Matt Ritchie, Dan Barlaser, Yasin Ben El-Mhanni (Ayoze Perez 70), Yoan Gouffran.
Birmingham City: Adam Legzdins, Josh Dacres-Cogley, Ryan Shotton, Paul Robinson, Jonathan Grounds, Maikel Kieftenbeld (Diego Fabbrini 80), Robert Tesche, David Davis (Reece Brown 64), Viv Solomon-Otabor (Lukas Jutkiewicz 64), David Cotterill, Che Adams.
Referee: Lee Probert
Bookings: Newcastle United – Cheick Tiote (69); Birmingham City – Adam Legzdins (9), Ryan Shotton (34).
