Change in Maternal Bone Mineral Density during the Former Period of Pregnancy：Its Relations with Bone Metabolism and Dietary Intake of Calcium and Protein

The purpose of this study was to examine the change in bone mineral density (BMD) during the former period of pregnancy, the relations with bone metabolism and dietary intake of calcium (Ca) and protein. In 52 pregnant women, BMD was measured three times first at 11-16 weeks of gestation, second at 24-28 weeks and third within one week postpartum by ultrasonic bone densitometry, and bone metabolic markers in urine and serum were measured at the same time. Intake of Ca and protein during three days, and Ca/protein intake ratio were respectively analyzed in relations with change in BMD during the former period of pregnancy and bone metabolic markers. Nutrient intake was adjusted by total energy intake. Stiffness calculated from the combined value of speed of sound and broadband ultrasound attenuation was used as an index of BMD. Two patterns of an increase and a decrease were found in BMD during the former period of pregnancy. The extent of a decline in BMD during all period of pregnancy was significantly lower in increase group than that in decrease group. Ca intake was positively associated with the change in BMD, whereas protein intake was negatively associated. Ca/protein intake ratio showed a significant positive effect on change in BMD． And Ca/protein intake ratio indicated significant positive correlations with serum Ca/phosphorus ratio and serum bone alkaline phosphatase／urinary N-terminal crosslinking telopeptides of type I collagen ratio at the second stage. These results suggest that the bone loss during pregnancy may be attenuated by a greater dietary ratio of Ca to protein in the former of pregnancy