[Effects of pregnancy and lifestyles including food intake on bone density of pregnant women].

Bone densities measured by ultrasound at the calcaneus, and urinary hydroxyproline (H.P) and calcium (Ca) concentrations adjusted for creatinine (Cre) were measured in 79 pregnant women, aged 20 to 38 years, at 5-40 weeks of gestation. Stiffness calculated from the combined value of speed of sound and broadband ultrasound attenuation was used as an index of bone density. The relationships between Stiffness and period of gestation, urinary H.P/Cre and Ca/Cre, and such lifestyles as current and past food intake frequency, physical activity and history of participating in sports obtained by questionnaire were examined using stepwise multiple regression analysis, including age and weight as independent variables. 1) The means of Stiffness in women with the gestation period of more than 20 weeks (primipara 79.6, multipara 83.4) are a little lower than those of non-pregnant and healthy women within the same age range. 2) Period of gestation showed a significant negative correlation to Stiffness. Significant positive correlations were found between urinary H.P/Cre and period of gestation. These results suggest that bone resorption increases with stage of gestation and causes bone loss in pregnant women. 3) Significant relationships with Stiffness was found only in frequency of cow's milk intake before pregnancy among various lifestyle factors. Stiffness of the subjects who took cow's milk every day before pregnancy was significantly higher than those who took less than 2-3 times per week or none. This result indicates that cow's milk and dairy products intake before pregnancy may be important for bone mineral maintenance during pregnancy.