ActionScript 3.0 :: Cannot Remove (Child) From Stage

I am trying to remove a swf that I import to the stage, but it is not working.
Code:
function btn_cima_3call(clickEvent:MouseEvent):void{
page = 5;
esconder();
content.gotoAndStop(page);
ld.load(new URLRequest("trabalhosV0.swf"));
ld.x = 0;
ld.y = 100;
addChild(ld);
}

So when 1 button is pressed this swf is imported to the stage. but im now trying to remove this when another button is pressed and it isnt working?
Code:
function btn1call(clickEvent:MouseEvent):void{
removeChild(ld);
page = 1;
content.gotoAndStop(page);}