I wonder what happened:

• staged / fake to imply option 2?
• actually expecting a child from the guy on the left, and proudly announcing it to her husband (mid) with this gesture?
• option 2, but only the husband (mid) knew, and he is announcing it to both
• option 2, everybody knows, but the parents didn't know that the husband knows, which he is announcing herewith (only option that explains ALL facial expressions)
• wanted pink smoke, but device malfunctioned / wrong device?
• both: the child is from the guy on the left, but it was supposed to be a secret to the grave, foiled by the chatterbox smoke device?

I honestly don't know.