Plasma calcium and magnesium in newborn babies.

Normal values for plasma calcium and magnesium levels during the first week of life, in breast- and bottle-fed babies, have been determined. It has been shown on the sixth day that plasma levels of calcium, magnesium, and protein are all significantly lower in bottle-fed babies than in breast-fed babies, while the reverse is true of the plasma inorganic phosphorus. The normal babies have been compared with 30 babies who had convulsions, beginning towards the end of the first week of life. In only six of the babies was the plasma calcium outside our normal range and only four had abnormally low magnesium levels. As so many of these babies had calcium and magnesium levels within the normal range it must seriously be questioned whether hypocalcaemia or hypomagnesaemia could have been the sole cause of the convulsions.