It depends on the total amount of Egg Cycles (255 steps) you have left until the Pokemon hatches.
>The number of Egg cycles that an Egg has left determines what is displayed on its status screen. When an Egg has more than 10 Egg cycles remaining, it will display, "Wonder what's inside? It needs more time, though." When the Egg's cycles have dipped below that, but are still above 5, it will display, "It moves around inside sometimes. It must be close to hatching." When the Egg has less than 5 cycles remaining, it will display, "It's making sounds inside! It's going to hatch soon!"
Note that the phrase used may differ from game to game, but should remain fairly similar.