A third of mothers introducing their children to te reo were not Maori.
Manukau mother Marama Davidson speaks "barely conversational" Maori and her husband Paul knows only "basic words" - but they speak te reo Maori to their young daughter Teina.
"Te reo is important to me and my family even though we don't all learn it," Ms Davidson said.
"It's a huge part of our identity and it's important for our whole collective nation to hold on to and treasure."
She has worked for the Human Rights Commission for nine years so her attitude to might be predictable.
But Growing Up in NZ study director Dr Susan Morton said one of the big surprises in the first post-birth interviews with parents, when their babies were nine months old, was that 16 per cent of mothers and 12 per cent of fathers spoke at least some Maori language to their babies.
Earlier interviews during pregnancy found that only 5 per cent of mothers and 3.5 per cent of fathers could hold a conversation in Maori.
Almost a quarter (24 per cent) of the study's 6846 babies were described by their mothers as Maori.
But 32 per cent of all babies had more than one ethnicity - 69 per cent were NZ European, 21.3 per cent Pacific, 16.9 per cent Asian, 2.8 per cent Middle Eastern, Latin American or African and 4 per cent other ethnicities.
Two-thirds of the mothers speaking Maori to their babies were Maori themselves, representing almost all of the 18 per cent of mothers who were Maori. But a third of those speaking te reo to their babies were not Maori.
However, English is still dominant. Asked which language they spoke most to the baby, 79.6 per cent of mothers said English and only 0.7 per cent said Maori.
Marama Davidson said she learned Maori at university and did not use it much with her first five children, who are now aged between 17 and 4.
But by the time Teina was born three years ago, she was inspired by seeing her brother, his partner and their four children speaking Maori fluently.
"In the past six months I have tried to speak only te reo to her. I feel more comfortable speaking to her than I would to other adults because I feel less judgment if I make mistakes."