Calcium Carbonate to Augment Labor Contractions

Eligibility Criteria

• * 18 years or older
• * Nulliparas (no prior pregnancy lasting 20 weeks or greater of gestation)
• * Gestational age above 36 weeks, at enrollment
• * Present for induction or augmentation of labor inclusive of medical indication, elective induction at greater than 39 weeks' gestation, trial of labor after cesarean
• * Singleton gestation (a multiple gestation reduced to a singleton, either spontaneously or therapeutically, before 14 0/7 weeks of gestation is acceptable)
• * Ability to give informed consent
• * Planned to undergo initiation of oxytocin infusion by their maternity care provider
• * Unable to understand or read English
• * Presence of tachysystole (defined as more than 5 contractions in 10 minutes averaged over 30 minutes), recurrent variable or late fetal decelerations, and bradycardia in the prior 30 minutes before enrollment
• * Non-vertex presenting fetus at enrollment
• * Planned for cesarean delivery or contraindication to labor by institutional policy (e.g., placenta previa, vasa previa, active genital herpes infection, previous transmural myomectomy)
• * Multi-fetal gestation (twins, triplets, and higher order multiples)
• * Known contraindication to taking calcium carbonate including renal calculus, high urine calcium levels, elevated serum calcium, low serum phosphate, achlorhydria, or suspected digoxin toxicity.
• * Deliveries with fetal chronic and/or pregnancy-related conditions, IUFD (Intra Uterine Fetal Death) or premature \< 36 weeks of gestation.
• * Major fetal anomaly suspected prenatally (defined as a fetal anomaly with anticipated neonatal intensive care unit admission)
• * Suspected alloimmunization (given the increased likelihood for anticipated neonatal intensive care unit admission)
• * Known severe fetal growth restriction (estimated fetal weight \<3rd percentile) or abnormal umbilical artery Doppler studies (given the increased likelihood for anticipated neonatal intensive care unit admission)
• * Participation in another interventional study that influences management of labor and delivery or perinatal morbidity or mortality
• * Known allergic reactions to synthetic oxytocin intravenous solution or to Calcium Carbonate
• * Significantly impaired consciousness or executive function (e.g., intubated or sedated)
• * Patients treated with calcium channel blockers such as nifedipine or magnesium.
• * Chronic renal failure and hyperphosphatemia.
• * Inability to tolerate oral intake (i.e., nausea/vomiting)