A new study suggests Vitamin D should be a supplement recommended to all pregnant women.
Babies with lower levels of Vitamin D at birth are twice as likely to be admitted to hospital with acute respiratory infections.
Olivia McLean is eleven weeks into the minefield that is motherhood. After giving birth to Julian she's been given screeds of information - the latest about Vitamin D supplements for her baby.
"My plunket nurse had advised me earlier in the week that it was new research that had come out from the Ministry of Health that Vitamin D reduced respiratory infections in new babies," she told Newshub.
Sunlight is a well-known source of Vitamin D - but sitting in it too long can be dangerous.
A new study by Auckland University suggests Vitamin D supplements help boost the baby's immunity before it's born and prevent a deficiency.
"Over half of babies at birth are Vitamin D deficient," Auckland University professor Dr Cameran Grant said.
Researchers looked at Vitamin D levels from just over 1000 babies at birth, and examined their respiratory admissions in their first year of life.
Those with a Vitamin D deficiency were twice as likely to end up in hospital with an acute respiratory infection.
"They can be breathing so hard that they can't feed and they can't sleep and simply can't get enough oxygen," Dr Grant said.
Māori and Pacific babies are more likely to have a deficiency and be hopsitalised with respiratory infections in early childhood.
A Vitamin D supplement could be a simple solution.
"The safest approach would be just for all pregnant women to be receiving the supplement as they do in other countries," Dr Grant said.
Rebecca Bateup is preparing for the birth of her second baby.
"We just take what's recommended and we'd do the same if Vitamin D supplement was recommended - that would be something I'd take," she said.
The new information is helping mums prepare for their little rays of sunshine.
