Her daughter is critically ill and it might result in the death of both her and her unborn child. Smiling at this time is highly inappropriate.
It would cause annoyance among the family, making further conversation impossible.
Zhou Can decided to tell the truth straightforwardly.
"Our department's director and attending physician are doing their best to make a diagnosis. However, as your daughter is pregnant, the diagnostic difficulty is significantly higher than usual, and we have only tentatively identified the lesion as potentially being within the cranium. Our Dean Zhu has already personally intervened in this matter, calling in doctors from some of the top departments for support. They should be arriving shortly."
Zhou Can intentionally informed the family that reinforcements were on the way, so they need not worry about the rescue team being understaffed.
This was also a form of reassurance for the family.