Mrs Waugh said law in Belgium, Germany, Hungary and Switzerland was for children to use restraints up to age 12 years old or 150cm. In Canada and British Columbia, Mrs Waugh said the age cap was at 10.
She hoped New Zealand would reach this stage eventually.
Mrs Waugh said the new law could be a problem for those with bigger families as they would need to cram more car seats into their vehicles.
"It's law in other countries and if they can cope with it we will have to as well."
She said Plunket was happy to help where it could with advice and handy pointers.
Tauranga mother Donna Tuck's 4-year-old son Korban will be one of the first children to be legally required to stay in a car seat or booster seat until he is 7.
Mrs Tuck said she supported raising the age.
"It's about time. It's good the age has gone up past 5, but I think it should be done on age rather than height, although that might be hard to police. Korban will stay in his booster seat with a harness until he is about 7 or 8, then he'll use the seat by himself until he's a bit older. My 9-year-old is still in a booster seat."
Senior Sergeant Ian Campion of Western Bay road policing said he supported anything that contributed to making occupants safer in vehicles.
Injuries received by children in car crashes in Tauranga
2008 - 9 (includes two deaths)
2009 - 1
2010 - 8
2011 - 4
2012 - 5
TOTAL - 27
Car seat laws
All children under 5 years old must use a child restraint (car seat or booster)
From November 1, the age will increase to all children under 7
Penalties are an infringement fee of $150 or a maximum fine of $1000 on summary conviction
Some countries require child restraints until 12 years old or until child is 150cm tall