Unfortunately, wanting to take care of your wife after your baby is born is an almost guaranteed reason for a TRV refusal because it is like working illegally even if it is unpaid.i applied for my mon in law come here to take care her daughter after her delivery ..but they reject her visitor visa
It does not matter if your mom-in-law is from Pakistan. Most visa offices refuse applicants from any country for the same reason.
This really has nothing to do with Pakistan applications. My advice is to make sure you/applicants must have a solid application + genuine purpose of visit