the utility of calcium balance in DRI development in pregnancy is complex, because the positive calcium balance achieved early in pregnancy is reduced to a neutral calcium balance or a slightly negative calcium balance by term.
Maternal BMD/fetal BMC/maternal fracture risk Neither AHRQ-Ottawa nor AHRQ-Tufts addressed calcium and bone health in pregnancy. Bone turnover is modestly increased from as early as the first trimester, and the analysis concludes there is inconsistent evidence that BMD may decrease between prepartum and postpartum measurements, as discussed above.
Olausson et al. (2008) reported 1 to 4 percent decreases in whole-body, spine, and total hip BMC and BMD from before pregnancy to 2 weeks postpartum compared with a nonpregnant, non-lactating group, but calcium intake was not related to this skeletal change. Thus, it is conceivable that some calcium provided to the fetus derives from the maternal skeleton during pregnancy. Calcium supplementation among Gambian women with low calcium intakes (355 mg/day) during pregnancy resulted in significantly lower maternal hip BMC and BMD and greater loss of bone mineral in the lumbar spine and distal radius compared with that found in the placebo group (Jarjou et al., 2010). The rate of increase in whole-body BMC is also slower in the breast-fed offspring of calcium-supplemented women during the first year (Jarjou et al., 2006). These two RCTs suggest no benefit to the fetus and possibly an adverse effect on the mother and infant, at least in the short term, of calcium supplementation during pregnancy. Further, the majority of epidemiological and prospective studies report that parity is associated with a neutral or even a protective effect relative to maternal BMD or fracture risk later in life (Sowers, 1996; Kovacs and Kronenberg, 1997; O’Brien et al., 2003; Chantry et al., 2004).
Thus, additional calcium intake during pregnancy does not appear necessary for maternal or fetal bone health. Similarly, pregnant adolescents, who are in an active period of bone accretion, do not have impaired BMD or increased fracture risk as reported in observational and large cohort studies (Sowers et al., 1985, 1992; Fox et al., 1993; Sowers, 1996; Kovacs and Kronenberg, 1997; Chantry et al., 2004). Thus, maternal and fetal BMD/BMC and maternal fracture risk have utility as an indicator for DRI development for pregnant adults and adolescents.
Hypercalciuria Most pregnant women are hypercalciuric with typical intakes of calcium (Gertner et al., 1986; Dahlman et al., 1994; Cross et al., 1995; Seely et al., 1997). This suggests that increased intakes of calcium could aggravate hypercalciuria as well as the