Encapsulated Calcium Absorption in Pregnancy

This study will enroll at least 60 pregnant women in a randomized cross-over study in Dhaka, Bangladesh. Each participant will be randomized to one of 3 calcium doses: 500 mg, 1000 mg, 1500 mg elemental Ca per day. Each participant will undergo two calcium absorption tests, one with a micronutrient supplement powder containing non-encapsulated (non-coated) calcium and the other with a micronutrient supplement powder containing encapsulated calcium at the same dose. The absorption tests will be separated by a 2-week washout period. Fractional calcium absorption will be measured using the dual stable isotope method. For each test, the formulation will be administered orally for 9 days; on the 10th day, a 44Ca- labeled stable isotope will be given orally and a 42Ca-labeled stable isotope dose will be given intravenously. Urine will be collected for 48 hours to measure calcium absorption.