Researchers have found more than half of Dunedin women and three-quarters of their babies are not getting enough vitamin D, potentially affecting their bone health and growth.
The University of Otago study published on Monday looked at 126 women attending Dunedin's Queen Mary Maternity Centre between 2011 and 2013.
It found 65 per cent of women and 76 per cent of infants were vitamin D deficient, with three of the children having rickets, a condition in which the bones soften and weaken.
Rickets can potentially lead to bowed legs and stunted growth among other complications.
Lead author Dr Ben Wheeler says the study indicates new public health measures may be needed, such as funding a vitamin D supplement to be given to all women and their children.
"This is particularly an issue in New Zealand as living further south potentially decreases one's ability to make vitamin D," he said.
Present public health policy only provides vitamin D supplements to pregnant women and breast-feeding infants considered at risk.
This includes those who have naturally dark skin, a sibling with rickets, liver or kidney disease and those taking medications which affect vitamin D levels.
But Dr Wheeler said the majority of New Zealand women and their children did not meet these risk criteria, while the new research showed vitamin D deficiency was even common in those previously considered low risk.
Previous studies had already demonstrated vitamin D supplements given during pregnancy significantly improved an infant's bone health at birth, he said.
A pregnant woman's ability to make vitamin D can vary with the season and latitude at which they live, their skin colour, what vitamin supplements they take and changes in their metabolism.