Within certain limits, pregnancy may prove positively beneficial to a woman. On the other hand there are conditions in which pregnancy will prove to be her undoing. There is a vigorous tendency of the embryo to maintain, at whatever cost to the mother, the calcium content of its own organism. This is the reason that the pregnant woman, inadequately supplied with lime salts, loses part of her teeth. In severe cases of deficiency, she may even develop osteomalacia.

There will be a loss of lime, iron and other elements from the pregnant woman's tissues unless her own diet is rich in these. The fetus behaves somewhat as a parasite if the mother is not well-fed. If the food is insufficient or deficient, or if other unhygienic factors disturb the mother's nutrition, the metabolic balance will become disturbed in favor of the fetus. Depletion of the maternal bone-calcium occurs where the mother's diet does not contain a sufficient amount of assimilable calcium. The feeding of inorganic calcium (lime water and other lime containing drugs) to the pregnant woman does not benefit.

Experiments with rats have shown that the calcium content of fetal rats remains normal when the mother's are inadequately supplied with lime salts. When the diet of female rats is deficient in calcium it does not affect the calcium content of the young rats unless the deficiency has persisted for a long time prior to pregnancy. If such prolonged deficiencies have existed, the entire development of the young is seriously impaired.

Dibblet, feeding diets very poor in calcium to pregnant dogs, found the skeleton of the new born dogs possessed a normal calcium content, although the mother invariably suffered with osteomalacia, so greatly had the vigorously growing fetuses robbed her blood and bones of lime to supply their own bone-building requirements. As much as 30 per cent of the calcium was withdrawn from the mother's bones.

Whether the fetus is to develop in harmonious symbiosis, or antipathetic symbiosis (parasitically) depends upon the mother's nutrition. It lies within the power of the mother to determine whether her child shall be a parasite or a symbion. She is eating and living both for her child and herself. Surely this is a subject worthy the study of every prospective mother.