The floor on which the babies are playing is not very stable and will start to break, when these break completely the babies could fall to their deaths!
To stop this from happening you must tap as fast as you can on decaying blocks to repair them.
But this alone will not always be enough because eventually you will have too many babies causing too much damage so you will lose some blocks.
What you need to do in this case is tap on a baby about to fall down to change his direction or tap on a baby that has already fallen to make him jump very high to help him get back on the blocks.
While you do this you should also tap on the broken block which can still be repaired but will stay broken until you repair it completely.
You will only lose if you completely run out of babies so use this knowledge to make smart decisions to keep playing and keep increasing that score!