Influence of moderate food restriction on calcium metabolism in pregnant rats

Two groups of female rats, non-pregnant (NP) and pregnant (P1), were fed ad libitum. A second group of pregnant rats (restricted diet, P2) were restricted for 14 d to the same intake as NP, and their ration was then increased by 5% from d 14 to d 21. For the first 3 d P1 and P2 absorbed a higher percentage of calcium than NP. During the final wk of pregnancy serum calcium decreased and 1,25-dihydroxycholecalciferol increased regardless of the dietary regimen. In both P1 and P2, femur calcium was higher than in NP on d 7 and apparent bone density increased during the 2nd wk of pregnancy and decreased from then on, this decrease being more pronounced in P2. On d 21, P2 fetuses were smaller and contained a smaller amount of calcium than those in P1, although the calcium concentration in the body remained similar in both groups of fetuses.