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Though osteomalacia is fundamentally a disease due to vitamin D deficiency and dietary calcium shortage, it is made manifest or aggravated by a host of predisposing factors among which the processes of reproduction deserve special attention. Pregnancy and lactation, albeit normal physiological phenomena, make additional demands upon the calcium and phosphorus supplies of the mother, so that diets adequate under ordinary circumstances become deficient during reproductive activity. Our previous reports (1, 2) on the metabolic data of eight Chinese lactating women, with or without osteomalacia, have demonstrated that the drain of lactation varies with the stage of lactation and the quantity of milk secretion. During late lactation when milk yield is small, positive balances in calcium and phosphorus can usually be secured with the addition of vitamin D, even when the intake of minerals is moderate or limited. However, in early lactation, especially if abundant, the loss of calcium in milk is so great that a high intake of calcium is essential in addition to adequate vitamin D supply to prevent depletion of skeletal store. Therefore, if nursing is maintained on dietaries deficient in vitamin D and calcium, as is often the case in China, skeletal demineralization will inevitably result. A similar chain of events probably occurs in pregnancy. In this part of the reproductive, cycle nutritional requirements are increased to provide building material for the fetus and its adnexa and for the development of maternal tissues such as the uterus, mammary glands and other organs, in order to meet the demands of labor and parturition and to prepare for milk secretion. The quantitative aspects of the question are not accurately known, but may be approached from the chemical analysis of fetuses at term and at various ages. Givens and Macy (3) and Macy and Hunscher (4) have shown the average calcium content of the human fetus at birth to be about 21 to 23 grams; Coons et al. (5) give similar estimates, while McIlroy (6) puts the figure considerably higher, namely, at 30 grams. The average phosphorus content of the fetus at term is approximately 14 grams. The whole subject has been reviewed by Macy and Hunscher (4) and by Garry and Stiven (7). It is generally accepted that the mineral needs of the fetus are insignificant during the first four months, but from then on they increase rapidly so that about two-thirds of the total are deposited during the last three months. Therefore, a minimum of 200 mgm. of calcium and 100 mgm. of phosphorus per day should be retained by the mother during the last three months of pregnancy in order to satisfy the fetal requirement without drawing upon the maternal mineral store. These estimates, though they are from Western sources, may serve to indicate the magnitude of drain upon the maternal tissues during pregnancy if living conditions and dietaries are incapable of supporting such a degree of mineral retention, as they appear to be frequently in China. The primary purposes of the work to be reported in the present communication are to observe the calcium, phosphorus and nitrogen metabolism of patients with osteomalacia during pregnancy, to compare it with that of individuals without skeletal decalcification and to assess the relative importance of vitamin D, calcium and phosphorus intake in securing adequate mineral balances for the added requirements of gestation.

CALCIUM AND PHOSPHORUS METABOLISM IN OSTEOMALACIA. XI. THE PATHOGENETIC RÔLE OF PREGNANCY AND RELATIVE IMPORTANCE OF CALCIUM AND VITAMIN D SUPPLY