It is not something to be taken lightly. Rose was very worried about Rune's mother's safety. It would be better if they visited after Finland gave birth to make sure that she was healthy and ready to meet guests.
Rose couldn't imagine herself in Alexis and Rune's shoes, it must have been worrying to see their aging mother being pregnant like this.
Meanwhile, Rune just smiled at Rose because he understood that this girl didn't know that their family members were immortal. Finland was not young for regular human standards, but she being pregnant was really not a problem. It's just that their parents would certainly have to make some efforts to prepare for childbirth and take care of the baby.
The last time they had a baby was over forty years ago, when Rune was born. So, whatever skills they had back then must be rusty and needed sharpening.