Risk of Rickets in Babies of Vitamin D-Deficient Mothers

The authors, Kate Thompson, Ruth Morley, Sonia Grover and Margaret Zacharin, conducted a study of women with vitamin D deficiency during pregnancy who had delivered their babies between August and October 2002 at the Royal Women's Hospital, Melbourne.

Vitamin D deficiency was defined as a 25-hydroxyvitamin D level of < 30 nmol/L. The study showed that most mothers who had been vitamin D-deficient in pregnancy were also deficient postnatally, indicating that treatment offered, counselling and/or treatment compliance were inadequate. Of 47 women who attended the postnatal follow-up clinic, 35 had been prescribed vitamin D supplements during pregnancy, but only 19 had taken them as prescribed. None continued to take the supplements after their babies were born.

Their infants, especially if breastfed, were at high risk of vitamin D deficiency and increased abnormal bone formation. Almost a third had vitamin D deficiency, a quarter had increased bone formation, and two had rickets. Twelve of the 16 breastfed infants had vitamin D deficiency compared with two of the 29 fed formula milk.

"It is doubtful whether either case of rickets would have been diagnosed apart from our audit, raising the possibility that rickets is more prevalent in high-risk populations than is generally appreciated," say the authors.

The authors strongly support breast feeding, but consideration should be given to vitamin D supplementation of breast fed infants.

Vitamin D helps the body absorb calcium, which is essential for healthy bones. We get 90 per cent of our vitamin D from skin exposure to ultraviolet B rays in sunlight. Prolonged vitamin D deficiency causes rickets in children and softening of the bones in adults. Vitamin D deficiency is particularly problematic in dark skinned women and their children, and among people with low skin exposure to sunlight.

CONTACT Dr Margaret ZACHARIN 03 9345 5522 (request page)

Judith TOKLEY, AMA Public Affairs, 0408 824 306 / 02 6270 5471