Pregnant New Zealand women should be taking vitamin D supplements to help ensure their babies are not at risk of rickets, a new study has found.

One in five New Zealand infants has a vitamin D level at birth low enough to put them at risk of rickets, the study found.

Breastfed infants of Maori or Pacific Island women - or infants of women with dark skin or who are often covered or veiled when outdoors - are at the greatest risk of having low vitamin D levels.

Rickets is a disease which causes soft bones in children that can lead to deformities and fractures.


Vitamin D deficiency has re-emerged as a public health problem around the world, said the study's author, Starship paediatrician Cameron Grant, an associate professor at the University of Auckland.

"New Zealand is a country that neither fortifies its food with vitamin D nor recommends vitamin D supplements be taken routinely, and so we have a higher rate of vitamin D deficiency than many other countries," Professor Grant said.

"We have shown in this study that if we want to achieve normal vitamin D status in babies in New Zealand we should be giving vitamin D supplements."

More than 90 per cent of our vitamin D is obtained from sunlight but it was impossible to use sunlight as a safe and reliable source of vitamin D throughout the year, Professor Grant said.

Beachlands mother of two Eileen Reid is expecting her third child in February. Her doctor advised her to take folic acid in her first trimester to guard against neural tube defects, and a daily iodine tablet throughout her pregnancy. Iodine deficiency has been linked to thyroid and brain development issues.

Mrs Reid also takes a pre-natal multi-vitamin that includes vitamin D. Her doctor advised her that taking the multi-vitamin wasn't necessary but there was no harm in taking it.

"It contains just about everything under the sun, I think," she said.

She was also conscious about getting out in the sun to help boost her vitamin D levels.

"I try to not wear sun screen out of the risky times."

The University of Auckland study was done in collaboration with Harvard University, the University of Otago, Kidz First Children's Hospital and Lead Maternity Carers Ltd.