If you have platy's that are ready, be sure to provide lots of hiding places - I found that java moss works really well when distributed in a corner of the tank. This way if the female has her fry, its harder for the other fish to try and eat it while trying to navigate through the moss.
My female just had babies ( only one has survived with all of the fish in my tank ) and this little fry is 2 or 3 days old but hiding nicely in the java moss.
This is a natural occurrence for us as the female usually has a batch every 4-6 months but only 1 fry ends up making it.
This picture is from another female last year but just to give you an idea of when they are ready. She gave birth the next day.
blurry photo but this is the fish that I think is soon to give birth