"We're not worried about that at the moment, we're just hoping that everything goes well for them. It's their first child so it's an exciting time for them."
Crusader Ryan Crotty is travelling as a back-up and will probably replace Fekitoa on the reserves bench.
Hansen added of the late disruption to his carefully laid plans: "We've had a few in the past. This is just another one. If you expect things to happen then you plan for them. Malakai started the last test match so he'll be fine and I'm sure Ryan Crotty is exciting about getting on the plane.
"It was a pretty big challenge last time too against England," Hansen said of the challenge in front of Fekitoa. "We've got every faith in him, he'll be fine. The game won't be won out there, it will be won up front. If we do things right up front it will be easy for him. If we don't do things right up front it will be tough for all of them."
Fekitoa was outstanding for the Highlanders this season. His test debut came against England at Eden Park when he played the final moments of the tight match, and he impressed in his start against England a fortnight later in Hamilton.
A quick learner with a cool head, Hansen will back him to slot in seamlessly with midfield partner Ma'a Nonu, but there is no doubt his opposite, the experienced Adam Ashley-Cooper, will look to exploit Fekitoa's inexperience. Smith, a defensive rock for the All Blacks, has played 77 tests.
Hansen is picking a boy weighing "about six pounds".