The authors administered a-preparation of vitamine D, called "Oryzae" 5g. a day to pregnant women during the latter 2-3 months of pregnancy, and took the blood at the time of delivery from the eubital vein, togather with the blood of the newborn taken from the umbilical vein. The inorganic phosphorus and the total calcium in the blood serum of the mother and the newborn were measured, as early as possible after delivery. The P content was measured after Kuttner-Cohen and that of Ca, after Kramer-Tisdall. The distal end of the newborn's ulna was revealed by X-ray and the appearance of the rachitic shadow was investigated. The cases experimented on amountet to 65. The results obtained were as follows: 1. The P content was more in the cases of vitamine D administration than the contrast, being 5,12mg.% on the average. 2. The bone shadow by X-ray photographing was less in number in the appearance of the so-called rachitic alteration than the contrast. 3, The P content of the newborns blood tended to rise during the summer, being always of higher rate than the contrast. In conculsion, the administration of vitamine D to pregnant women is believed to protect the rachitis or rachitis-like state of the newborn, when given continously in the latter period of pregnancy.