But for Illawarra four-year-olds Imogen, Digby, Jensen, Isaac, Adam, Jay, Josh, Isabelle and Rixen, those are problems for mum.

The children, whose mothers are members of the same Corrimal parenting group, are bonded by an annual photographic tradition that is much a feat of stage management as of calendar coordination.

The result is a fascinating and growing display of time in motion, with each child captured in the same order year-on-year, their changes benchmarked against their peers.

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The tradition began with a cake smash-themed shoot when the babies were turning one.

"That first year, they didn't know what was going on, and some were screaming, going 'why have you put this weird thing in front of me?' - not knowing what cake was," said group member and Mercury photographer Anna Warr, whose job it is to take the shot each year. "But it was easier in that they stayed put. As they got older the issue was getting them to stay still."

"The second and third year, we had them seated so that made it a bit easier, but by the fourth birthday, there was quite a bit of wandering happening. That was the most challenging, actually."

The photos are the result of a military-like planning operation that begins weeks in advance.

In the lead-up to each birthday season, hundreds of messages go back and forth between the mums, organising a date, time and finer details of props and location.

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On year one, one mum made a cake for each baby to smash. Another stitched a colourful "1" onto nine bodysuits. Some mums are good at making sure the kids stay in the same order each year; others have become efficient prop-distributors.

"It's actually pretty quick and efficient to take the photo because everyone's planned for it," Warr said.

"Its' a team effort.

"These mums are very active - a group of doers."

A one-time department store Santa photographer, Warr has learnt not to sweat it when a cardboard hat droops or a little face crumples into tears at the key moment.

"I kind of embrace that because it's more interesting than if they're all happy all at once," she said.

"I think it's just super nice to have a visual record of how they grow and change over time."

Parenting groups are run by the Illawarra Shoalhaven Local Health District to give new mums and dads the chance to support one another and share knowledge. They are initially led by a nurse, before the parents make their own meet-up arrangements.

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