"You would expect to see an increase in utilisation of health services ... the 'worried well' may end up going a lot," she said. "We may not necessarily get an increase in the at-risk group that we do want to see going more."
There were many reasons a parent wouldn't take their child to the doctor, such as transport difficulties and finding a child minder for other dependants, she said.
There would definitely be positive benefits of the programme, however, she said.
"A mother of a child who might have thought they'd 'wait and see', rather than taking their child to the GP, might end up taking them sooner," she said.
"It should also free up the emergency department slightly. Often families from low income households will go to [the emergency department] because they don't have to pay."
The programme is expected to benefit about 400,000 children nationwide. It will also include a contribution from ACC, which will mean about 213,000 children will receive free injury-related doctors' visits, according to ACC minister Nikki Kaye.
Doctors' visits are currently free for children under 6 years at about 98 per cent of New Zealand practices.