Eighteen-month-old Molly squirms and bursts into tears at the sight of Santa.

"She's scared, she's always scared of Santa," says Molly's mother Tina Lou, as she hands her daughter to her mother Mrs Wang.

The three generations are at a playgroup for the Mandarin-speaking community in Clayton, a suburb in Melbourne's south-east.

It's the final session of the year and the theme is Christmas.

Mrs Wang with her granddaughter Molly at playgroup. ( ABC News: Sally Brooks )

December 25 is not celebrated in a traditional way by many people from Chinese backgrounds.

But most people here, including Mrs Wang, are in the festive spirit.

The 58-year-old hates planes but has flown thousands of kilometres from a rural area in mainland China to Australia to help care for her granddaughter Molly.

"This is what love is all about," she says.

Mrs Wang has had to temporarily give up her own hobbies to come to Australia — she's a prize-winning amateur dancer back home — but it's a sacrifice she's happy to make.

"This is our responsibility. It is a little tiring, but this all transforms to happiness eventually," she says.

Tina Lou is "deeply touched" by her mother's effort to help care for her family.

"She came across the ocean to see me."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 56 seconds 1 m 56 s Santa makes an appearance at the final gathering of a playgroup near Melbourne.

Grandparent childcare worth $4.4b a year

Grandparents like Mrs Wang play an invaluable role caring for grandchildren in families across Australia.

That childcare can be even more helpful as the school holidays start.

In 2017, nearly 865,000 children were cared for by a grandparent for an average of 10 hours in a usual week in Australia, according to the most recent Australian Bureau of Statistics (ABS) data.

The total hours spent caring for grandchildren in a typical week was 8.8 million hours.

"Using a very simple model that assumes replacement cost based on the average cost of formal child care in Australia (excluding in home care), this equates to $84 million in a usual week, or $4.4 billion a year," the ABS said.

Grandparents in migrant families are a valuable source of childcare, according to researchers. ( ABC News: Sally Brooks )

But migrant grandparents are likely to be underrepresented in statistics and research, according to Dr Myra Hamilton from the University of New South Wales (UNSW).

Dr Hamilton is part of team at the UNSW running a study on migrant grandparents from China, Vietnam and Nepal.

"We are finding so far that grandparents are highly important as a source of childcare in the migrant families we have spoken to," Dr Hamilton said.

"Smaller qualitative studies … reveal that the contributions of grandparents to childcare in migrant families are extremely valuable.

"These studies suggest that migrant grandparents are more likely than non-migrant grandparents to emphasise the importance of passing on culture and language to their grandchildren, and to view their role as important in supporting their adult children to adapt to Australian society."

The UNSW study is focussing on Chinese, Vietnamese and Nepalese grandparents "because we wanted to interview grandparents who were on different visa types and citizens of countries with diverse migration histories in Australia," Dr Hamilton said.

'That is the Chinese way'

Linda Hsia is happy to look after her grandchildren. ( ABC News: Sally Brooks )

In some migrant communities, like the Chinese community, tradition and culture mean grandparents are often expected to lend a hand with grandchildren.

Linda Hsia has six grandchildren and helped look after them all.

Originally from Taiwan, she has lived in Australia for more than 40 years of her life, and feels "fair dinkum Aussie".

She said many grandparents from mainland China were perceived to work like "slaves" in the family home, doing a large amount of domestic work including shopping, cooking and cleaning.

"But that is the Chinese way, they don't feel 'oh I'm the slave to the family'," Mrs Hsia said.

"It's just 'I'm a member of the family, now it's my turn to look after the grandchildren'.

"You want to see them growing up happily, so I never really feel I was asked to do this or do that, I am too glad to do things for them.

"Every … group of people likes to pass on their own experiences, especially … Chinese."

'We have combined the best of both cultures'

Lee Xia often makes dinner for her son's family at their home in Melbourne's east. ( ABC News: Sally Brooks )

Lee Xia is originally from Beijing but has lived in Australia for more than 20 years.

"Back in China, grandparents are obligated to look after grandchildren. It is almost expected," she said.

"[But]…this is actually a privilege."

Mrs Xia would never refuse a request to help care for her grandchildren, but has managed to strike a balance between her personal and family life.

"I have a part-time job, sometimes I go out with my friends, we have a holiday each year."

She and her husband live with her son's family in Kew East near Melbourne.

"We have certainly accepted the influence of western culture more or less. So we have combined the best of both cultures," she said.

"To me, I will definitely not devote all my day to look after my grandchildren, cooking, shopping and household chores."