New York - Softening of the skull bones in normal-appearing newborns is tied to a vitamin D deficiency in the womb, according to Japanese researchers.
They suggest that breast-fed infants with this condition may need vitamin D supplements.
Soft skull bones, also known as craniotabes, in normal newborns is usually regarded as no cause for alarm, but Dr Tohru Yorifuji at Kyoto University Hospital and colleagues dispute this in their report in the Journal of Clinical Endocrinology and Metabolism. They point to evidence that the condition is associated with type 1 diabetes, reduced bone mass during childhood, and lowered immunity.
In their study, the researchers screened 1120 normal infants at five to seven days of age. Craniotabes was considered present when "the skull bones reversibly bended by application of pressure by the examiner's fingers".
They found that 246 babies, or 22 percent, had craniotabes. The highest rate occurred among infants born in April and May, and the lowest in those born in November.
Vitamin D production in the body is triggered by sunlight, and Yorifuji's team points out that the rate of craniotabes "was influenced by the daylight hours approximately four months prior to delivery". They say this strongly suggests that "the condition is associated with vitamin D deficiency in utero".
Low vitamin D levels and other abnormalities at one month of age were more common in babies who were breast-fed than in those who were fed formula at least part of the time, the investigators found.
They therefore recommend "treating breast-fed infants with craniotabes with vitamin D, or preferably, treating all pregnant women with vitamin D".