Calcium metabolism in pregnancy

Association between calcium in cord blood and newborn size in Bangladesh

Ca status in the uterus during pregnancy has been suggested to affect fetal growth and size at birth. In Bangladesh, low Ca levels in pregnant women and low birth weight in infants are common. The present study explored the association between Ca levels in cord blood and newborn size at birth (birth weight and birth length) in Bangladesh. Samples and data included 223 women with live-born singleton deliveries in rural Bangladesh. Newborn weight and length were measured at birth. From cord blood obtained at delivery, Ca, 25-hydroxy vitamin D, bone-specific alkaline phosphatase and intact parathyroid hormone levels were determined. An association between size at birth and Ca levels in cord blood was found (birth weight, P = 0.022; birth length, P = 0.001). Associations between Ca and newborn size were further analysed using multivariate regression analyses. After adjusting for several covariates of characteristics in mothers and newborns (gestational weeks at birth, sex of newborn, socio-economic status, maternal height, BMI, age and season at birth), birth length still exhibited a significant relationship with Ca levels in cord blood (birth length, P = 0.030). The present study indicates that Ca status in cord blood might be associated with the birth length of newborns. Ca levels during gestation may affect fetal growth.

Dose to red bone marrow from natural radon and thoron exposure

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about 16 times that in tissue. The mean dose equivalent muSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 microns, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly, the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miner and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq/m3 and an equilibrium equivalent thoron concentration of 0.3 Bq/m3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 muSv, respectively. For a 10-year-old child, the radon and thoron derived annual dose are 70 and 40 muSv, and for a 40-year-old adult 90 and 30 muSv, respectively. The above values exhibit wide range limits due principally to uncertainties in the accumulation of 210Pb in bone, and 210Po in marrow. These data indicate that at the average UK exposure, the alpha-particle dose to active marrow is dominated by that derived from inhaled radon and thoron compared with dietary intake. In infants the dose is dominated by thoron daughters. At the UK radon Action Limit of 200 Bq/m3, the radon and associated thoron derived dose is similar to that from all low LET sources. This work shows that the dose to red bone marrow from radon and thoron is significant, and that the possibility of leukaemia induced by these radiation sources warrants further investigation.