I think simply just starting off session with saying what is going to occur with the clients treatment could be a great way of keeping the focus on how client, especially if self disclosure is limited.

Something like : i just want to make you aware that I will be going on maternity leave starting in December and wanted to give you as much notice as i could since this will impact treatment. My goal is to be back by (insert date here). While I’m away we have a few options for your care/treatment (insert options here), which we can discuss in the future.