Ears
Ever since the baby was born she seems to have preternatural hearing. Before he can even detect the slightest whimper she's up checking on their son. Sometimes he swears she's imagining it and tells her to go back to sleep, that she's dreaming. Then he'll hear the cry and realize she was right all along even as she's heading for the nursery door.
The upside to all this is that he has far less middle of the night responsibilities.
The downside to it is that he can no longer sneak in late after he's been out drinking with Inoichi and Chouza.
