It is recommended that you should not interact with other 3rd party apps unless they provide a handle to interact. Which is already given by whatsapp as openurl scheme.
In case you have the contact that is removed or added you should address the issue first in your app so it doesn’t/does initiate the action to open App before evening checking with wahtsapp.
You can use a great library that APAddressBook to do the contact add and modified check.