Instantiate Prefab in location

I am trying to instantiate an object in the center of a scene but when score is reached nothing happens.

public Transform Prefab;

void Start () {
	if (GameControl.control.stat >= 10) {
		Instantiate (Prefab, new Vector3 (0, 0, 0), Quaternion.identity);

	}
}

@Youri1er : By doing this, the instantiation will occur each frame.

@soof :

private bool prefabInstantiated = false ;

void Update()
{    
    if (GameControl.control.stat >= 10 && !prefabInstantiated ) {
        Instantiate (Prefab, new Vector3 (0, 0, 0), Quaternion.identity);
        prefabInstantiated = true ;     
    }
}

You try to instantiate in the start function, try to move the test in the update function.