The 12-week-old baby girl, Ayla, was the sole survivor of a tragic car accident that killed her father Collins and mother Alana Madill in France on June 5.
French news website H-24 reported Ayla underwent a "long and delicate" cranial surgery on Tuesday at the University Hospital Centre in Montpellier.
She was then put in an artificial coma, which was believed to be a typical procedure after an operation of that kind, to reduce brain swelling.
Doctors would advise on her state within 48 hours of the operation and her condition remained critical.
The investigation into the deaths of Collins and Ms Madill, who came from Saskatchewan in Canada, continues in France.
The car accident occurred as the trio were driving home from an event at 3.10am French time along the A9 motorway near Beziers, in the south of France.
French police said they believed Ms Madill, the driver, had missed the turnoff on the A9 motorway to Narbonne.
Emergency workers said the car stopped by the side of the road, before attempting to pull back into the traffic, when it was hit by a bus with 21 people on board.
The car was apparently thrown about 10 metres.
Last week more than 3000 mourners, including rugby greats Jonah Lomu and Tana Umaga, attended Collins' funeral in Porirua's Te Rauparaha Arena.
Among them were Ms Madill's father Darrell, and sister Nora.
