text: Bendtner required oxygen as he was carried off the field on a stretcher, having landed awkwardly in a collision with Blues defender Michael Morrison.
  The Dane had set up Eric Lichaj to open the scoring and Apostolos Vellios made it 2-0 from Henri Lansbury's cross.
  Lukas Jutkiewicz headed a goal back for Blues but Hildeberto Pereira finished Ben Osborn's low pass to seal victory.
  A Birmingham win could have taken Gary Rowett's side as high as second in the table, but their first away loss of the league campaign means they may be outside the top six by the time they host Rotherham on Tuesday.
  Lichaj's powerful angled shot, the defender's first goal for almost a year, lit up a flat first half at the City Ground.
  The only other talking point before the interval was Lansbury's disallowed free-kick, with referee Jeremy Simpson initially awarding a goal and then reversing his decision following consultation with his assistant.
  Forest's win came hours after owner Fawaz Al Hasawi announced he is close to agreeing a deal to sell the club.
  Al Hasawi, who took control of Forest in 2012, would not reveal the identity of the buyers but BBC Sport understands that a United States consortium, led by millionaire John Jay Moores, is on the verge of securing a £50m deal.
  Head coach Philippe Montanier told BBC Radio Nottingham: "I enjoyed the victory. We've worked hard during the international break and we applied what we worked on during that period.
  "Bendtner's injury is a bad point of this evening. We don't know how serious it is. I hope it is not very serious.
  "When you go off on a stretcher, you always worry. We hope to have more news on Saturday."
  Birmingham manager Gary Rowett told BBC WM: "We weren't anywhere near the standards we've set so far this season, certainly in the first half. We were a little bit too predictable.
  "We wanted to do much better in the second half and there was a real determination to do that. We ended up at 2-1 and we looked as though we had put them under some real pressure.
  "I wasn't overly happy with one or two decisions, but I thought Forest deserved it. They showed more energy and desire."
  Match ends, Nottingham Forest 3, Birmingham City 1.
  Second Half ends, Nottingham Forest 3, Birmingham City 1.
  Henri Lansbury (Nottingham Forest) wins a free kick on the left wing.
  Foul by Stephen Gleeson (Birmingham City).
  Foul by Ryan Shotton (Birmingham City).
  Eric Lichaj (Nottingham Forest) wins a free kick on the left wing.
  Foul by Lukas Jutkiewicz (Birmingham City).
  Thomas Lam (Nottingham Forest) wins a free kick in the defensive half.
  Attempt saved. David Cotterill (Birmingham City) right footed shot from a difficult angle and long range on the left is saved in the top centre of the goal.
  Hildeberto Pereira (Nottingham Forest) is shown the yellow card.
  Diego Fabbrini (Birmingham City) wins a free kick on the left wing.
  Foul by Hildeberto Pereira (Nottingham Forest).
  Diego Fabbrini (Birmingham City) wins a free kick on the left wing.
  Foul by Hildeberto Pereira (Nottingham Forest).
  Attempt missed. Henri Lansbury (Nottingham Forest) right footed shot from outside the box misses to the left. Assisted by Ben Osborn.
  Attempt missed. Clayton Donaldson (Birmingham City) right footed shot from outside the box is too high. Assisted by Reece Brown.
  Foul by Ryan Shotton (Birmingham City).
  Ben Osborn (Nottingham Forest) wins a free kick on the left wing.
  Foul by Reece Brown (Birmingham City).
  Chris Cohen (Nottingham Forest) wins a free kick in the defensive half.
  Substitution, Birmingham City. Reece Brown replaces David Davis.
  David Davis (Birmingham City) is shown the yellow card for a bad foul.
  Foul by David Davis (Birmingham City).
  Eric Lichaj (Nottingham Forest) wins a free kick on the left wing.
  Foul by Ryan Shotton (Birmingham City).
  Chris Cohen (Nottingham Forest) wins a free kick on the left wing.
  Goal!  Nottingham Forest 3, Birmingham City 1. Hildeberto Pereira (Nottingham Forest) right footed shot from the centre of the box to the bottom left corner. Assisted by Ben Osborn with a cross.
  Substitution, Nottingham Forest. Thomas Lam replaces Mustapha Carayol.
  Foul by Ryan Shotton (Birmingham City).
  Chris Cohen (Nottingham Forest) wins a free kick in the defensive half.
  Foul by Clayton Donaldson (Birmingham City).
  Vladimir Stojkovic (Nottingham Forest) wins a free kick in the defensive half.
  Paul Robinson (Birmingham City) is shown the yellow card for a bad foul.
  Foul by Paul Robinson (Birmingham City).
  Mustapha Carayol (Nottingham Forest) wins a free kick on the right wing.
  Substitution, Nottingham Forest. Hildeberto Pereira replaces Armand Traore.
  Attempt missed. Michael Morrison (Birmingham City) header from the centre of the box is too high. Assisted by Lukas Jutkiewicz with a headed pass.
  Corner,  Birmingham City. Conceded by Vladimir Stojkovic.
  Attempt saved. Clayton Donaldson (Birmingham City) right footed shot from a difficult angle on the right is saved in the bottom left corner.
  Diego Fabbrini (Birmingham City) wins a free kick in the defensive half.
target: Nottingham Forest beat Birmingham but their 3-1 win was marred by an injury suffered by striker Nicklas Bendtner.