Interrelationships of calcium, phosphorus and glucose levels in mother and newborn infant

Intra-uterine long bone growth in small-for-gestational-age infants

To better understand the intra-uterine bone modelling and remodelling process in small-for-gestational-age (SGA) newborn infants, long bone growth was studied using postmortem X-ray films in a group of such infants (n = 34). Bone length, diaphyseal diameter, medullary diameter, cortical thickness, cortical area, the Barnett-Nordin index, and the percentage of cortical area were determined in femur, tibia, and humerus. A separate group of appropriate-for-gestational-age (AGA) newborn infants (n = 146) was used as controls. Length and cortical bone mass in all three bones were significantly lower in SGA infants than in AGA infants. Decreased cortical bone mass in SGA infants was the result of decreased diaphyseal diameters and increased medullary diameters. Similar results were obtained when SGA infants were subclassified as preterm and term and compared with the control group of AGA infants. Bone lengths and diaphyseal diameters in SGA infants did not differ from those observed in a weight-matched control group of AGA infants although the latter were younger by 4 weeks' gestation. However, the cortical bone mass was lower than in the control group because of the relative greater medullary diameters in all three long bones in the SGA infants. Our present results indicate that reduced cortical bone mass in SGA infants is a mixed growth modelling and remodelling dependent process.

Response of protracted neonatal hypocalcaemia to 1alpha,25-dihydroxyvitamin D3

Six infants with protracted hypocalcaemia (5 classed as tetany of the newborn) had a mean plasma-calcium of less than 6-4 mg/dl and raised plasma-inorganic-phosphate. Four had been hypocalcaemic for longer than 2 weeks despite treatment with low phosphate formulae and extra calcium. All the infants were treated with 1alpha,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), usually in a dose of 0-05 mug/kg body-weight/day, administered intravenously for 5--12 days. The plasma-calcium levels began to rise within 24 h after starting 1alpha,25-(OH)2D3 treatment, increased above 7-5 mg/dl within 3 days, and reached the normal range within 8 days. Four of the infants remained normocalcaemic when 1alpha,25-(OH)2D3 was discontinued, but two infants became hypocalcaemic again and required long-term treatment. 1alpha,25-(OH)2D3 has been found safe and dependable as treatment for protracted neonatal hypocalcaemia.

Normal total plasma calcium in the newborn

The first week of human life is characterized by rapidly changing plasma calcium levels, as well as low concentrations in comparison with adults. Whereas the infant's cord blood has a higher concentration than the mother's blood, the level drops precipitously in the first 24 hr (first drop) after birth and reaches a minimum level (second drop) at about 48 hr. A third drop may follow between the fourth and seventh days, but is different from the other two in that it is generally preventable with proper milk feeding. The level is markedly influenced by starvation, diet, and age. During the first week, the full-term newborn may show calcium levels in the range of 1.75 to 3.00 mmol/1, whereas the premature newborn shows values of 1.50 to 2.50 mmol/1. The low birth weight infant displays intermediate values. The literature on diseases involving calcium in the newborn, particularly neonatal tetany, is especially helpful in establishing a concept of normal levels, providing clinically supported upper and lower values. Calcium studies on the new born have been notably advanced by use of sound ultramicrochemical analytical methods.

Calcium metabolism in pregnancy: a review

Calcium metabolism in pregnancy is a complex process involving calcium, phosphorus, vitamin D, parathyroid hormone (PTH), and calcitonin (CT). Calcium absorption is enhanced in pregnancy, and increased storage in the maternal skeleton probably occurs as well. Adequate amounts are provided by the current Recommended Dietary Allowance of 1,200 mg. daily which can be met readily by natural foods, specifically milk. If supplemental calcium is given, a nonphosphate salt is probably advisable, since some evidence suggests that excessive phosphate intake may be related to leg cramps in pregnancy. Vitamin D is necessary for optimal calcium utilization in pregnancy, although the possibility of fetal toxicity with overdosage has been suggested. From a review of available information with respect to maternal-perinatal calcium interrelationships, I propose the following hypothesis: While total maternal serum calcium declines during pregnancy because of the physiologic hypoalbuminemia, the level of ionic calcium remains constant, in part, at least, because of increasing maternal PTH output. The placenta plays a primary role in fetal calcium metabolism by transporting calcium ions from the mother to the fetus against a concentration gradient. Relatively high fetal ionic calcium levels cause suppression of PTH and stimulation of CT in the fetus, facilitating growth of the fetal skeleton. With sudden loss of the placental source of calcium at birth, the newborn infant becomes functionally hypoparathyroid and/or hypercalcitonemic, and the serum calcium level declines until 3 to 4 days of life when PTH rises and CT falls with a resultant slight rise in calcium.

Neonatal convulsions associated with primary disturbance of calcium, phosphorus, and magnesium metabolism

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