A Kyoto University Hospital studied more than 1100 newborns in Japanese hospitals and observed that pregnancies over winter could lead to problems in babies.
Dr Tohru Yorifuji who led the research team said, "Craniotabes, the softening of skull bones, in otherwise normal newborns has largely been regarded as a physiological condition without the need for treatment."
"Our findings, however, show that this untreated condition may be the result of a potentially dangerous vitamin D deficiency."
The researchers found that 22 per cent of babies studied had craniotabes. It was also observed that the incidence of craniotabes was highest in babies born in April-May. Since these babies were carried in the womb in the winter months it is possible that their mothers lacked enough vitamin D, which is absorbed from sunlight.
Babies born in November had the lowest incidence of craniotabes, possibly because their mothers had a steady supply of vitamin D in the summer months when they carried the babies in their wombs.
"Otherwise, the incidence of craniotabes was not significantly related with the maternal age, number of pregnancies, birth weight, or weeks of pregnancies," said the researchers.
Dr Yorifuji said mothers should take care to ensure that their babies get sufficient vitamin D while feeding.
"Until more research is done on the effects of perinatal vitamin D deficiency, we suggest treating breast-fed infants with craniotabes with vitamin D, or preferably, treating all pregnant women with vitamin D," Dr Yorifuji said.
According to the research paper to be published in the May edition of the Journal of Clinical Endocrinology & Metabolism
, persistent vitamin D deficiency can lead to skeletal problems, as well as to higher risks of diabetes and colon cancer.