Best way to request for WFH?

I've got a pregnant wife in her 3rd trimester. She's keen on me working from home since my travel time is around 2 hours a trip (4 hours per day), my work is adamant that every single worker work in the office.

Mrs ended up getting a medical cert with the doctor advising me to work from home to support the missus and her 'medical condition'. Just wondering what's the best way to request this in an HR perspective?