In order to monitor WhatsApp messages on the non-jailbroken iPhone firstly iCloud back up for WhatsApp should be activated.
In order to activate WhatsApp back follow next simple steps:
Step 1: Open WhatsApp application > go to Settings section and select Chats;
Step 2: Tap Back Up Now to make manual back up .
Step 3: Click on Auto Back up and choose Daily in the list.