Association of Oedema and Hypomagnesaemia with Hypocalcaemic Tetany of the Newborn

The cases of 18 babies with hypocalcaemic tetany of the newborn are described. Studies were made before and 24 and 48 hours after therapy with calcium supplements. Twelve of the babies were non-oedematous and showed a positive correlation between serum calcium and magnesium levels. They showed a rise in serum magnesium levels during therapy with calcium. The other six had bilateral pitting oedema of the feet and greater weight gains in the first two weeks of life. They had abnormally low serum magnesium levels which did not correlate with the calcium levels. Furthermore, the serum magnesium levels, unlike those in the non-oedematous group, did not increase when calcium supplements were given. It is suggested that oedema in babies with hypocalcaemic tetany may be more common than is generally recognized, and that a contributory factor in the production of the hypomagnesaemia may be secondary aldosteronism.