How to tell girlfriend’s parents about pregnancy after just meeting them?

I'm a foreign resident, 33M. I met my girlfriend’s parents for the first time over New Year’s. We’re not married, and now she’s pregnant.

We plan to get married in future. She's planning to visit and tell them this weekend. I don't know if I'm supposed to say something afterwards (either on the phone or in-person; my Japanese is basic anyways)

For people who’ve been through this, what's the best way to go about it?