Pharmacokinetics of Oral Calcium Carbonate in Parturients

Inclusion Criteria: * Pregnant female subjects at the study institution, admitted for labor (spontaneous, augmented, or induced) Exclusion Criteria: 1. severe range blood pressure (BP \>160/\>110) within the 48 hours prior to delivery 2. patient age \<18 years or \>45 years 3. renal dysfunction with a documented serum Cr \> 1.0 mg/dL 4. known history of congenital or acquired cardiac disease or history of arrhythmia 5. patient taking digoxin 6. patient currently taking a calcium channel blocker 7. Weight \<55kg or \>100kg, or 8. receiving magnesium infusion within 24 hours prior to or during cesarean delivery 9. Prior or planned administration of calcium by the obstetric or anesthesiology teams for clinical indications within 24 hours of study enrollment 10. Patient took a calcium supplement in the past 48 hours 11. Patient status is NPO (nothing by mouth) as ordered by the clinical team