Research shows alarming rates of vitamin D deficiency in South Island women and their babies.

The University of Otago study, the first of its kind in the southern hemisphere, looked at 126 mothers and babies.

They found 65 percent of mothers and 76 percent of infants had high rates of vitamin D deficiency, largely blamed on lack of exposure to sunshine.

Otago University Senior lecturer, Dr Ben Wheeler said they found three babies with severe deficiency had developed rickets.

"That causes damage to the bones, thinning of the bones and at its worse cases it can cause seizures and developmental problems."

He said public health guidelines need to be changed to encourage more mums to take supplements.