Disclaimer: I don't own much, probably none.
Being a dad means holding your wife's hand for five hours because she asks you to. Even if your hand turns white and loses all feeling.
Kiba had a lot more upper arm strength than he gave himself credit for. The Inuzuka clan was famous for their ninjustus but they could pack a punch when they really wanted to. Like labor. Holy shit, Kiba was hiding some serious biceps underneath all those fur jackets.
Shikamaru decided to be a good husband, mainly because he feared Tsume had sensory super-powers when it came to her children, and let Kiba hold his hand. Wasn't it the kind of things that brings forth the image of childbirth? It was a very noble thing to do. Even if your hand did turn a shade of pale that made Sai's skin tone seem healthy and you were pretty sure your nerves had shut down.
It was the most troublesome part of childbirth for the father.