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Uterine ContractionPhase 2/3NCT07056062

Oral Calcium Supplementation in Labor

A Phase 2/3 study testing Calcium carbonate in people with Uterine Contraction and Labor Complication, run by Arrowhead Regional Medical Center at 1 site in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

The goal of this clinical trial is to learn if oral calcium carbonate can improve uterine contractions and labor outcomes in term pregnancies. It will also evaluate the safety of calcium carbonate when used during labor. Read more about this study

Who is it for?
Ages 18 years and older, women only
What is being tested?
Calcium carbonate
Could I receive a placebo?
No, everyone receives an active treatment
How many people
89 participants
Where
1 siteUnited States
Study dates
30 Apr 2024to 30 May 2025
Phase
Phase 2/3
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • Women only
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Had an intrauterine pressure catheter in place
  • Term gestation, greater than or equal to 37 weeks of gestation
  • Singleton pregnancy
  • Cephalic presentation
  • > 18 years of age

Who cannot join

  • incarceration
  • multiple gestation
  • active illicit drug use
  • abnormal clinical pelvimetry
  • Suspected fetal macrosomia defined as estimated fetal weight ≥4250 grams
  • intrauterine growth restriction
Show all 14Show fewer
  • abnormal placentation
  • prior cesarean delivery
  • maternal history of arrhythmia
  • hyperparathyroidism
  • heart failure
  • renal or hepatic failure
  • nephrolithiasis
  • receipt of medications known to affect uterine contractility-such as magnesium sulfate, terbutaline, or recent misoprostol in the last four hours

Trial locations and contacts

1 site in 1 country.

United States1 site

  • Arrowhead Regional Medical Center

    Colton, California, 92324

Other trials in United States

About this study

Official title: Effect of Oral Calcium Carbonate on Uterine Contractility and Labor Outcomes: A Randomized Controlled Trial

The goal of this clinical trial is to learn if oral calcium carbonate can improve uterine contractions and labor outcomes in term pregnancies. It will also evaluate the safety of calcium carbonate when used during labor. The main questions it aims to answer are:

Does oral calcium carbonate increase uterine contraction strength? Does it lead to shorter labor duration or higher vaginal delivery rates? What side effects or complications, if any, occur with calcium carbonate use during labor?

Read more

Researchers will compare oral calcium carbonate to no treatment to see if it helps improve labor efficiency and reduce cesarean delivery rates.

Participants will:

Be randomly assigned to receive either 2,000 mg of oral calcium carbonate or no intervention Undergo monitoring with an intrauterine pressure catheter to measure contraction strength Be observed for two hours without oxytocin to assess calcium's direct effect on contractions Have data collected on labor progression, delivery outcomes, and neonatal health

Read the detailed description

In the United States, nearly one-third of deliveries are performed via cesarean section, with labor dystocia remaining a leading indication. Labor dystocia may result from a variety of maternal and fetal factors, including malposition, cephalopelvic disproportion, or ineffective uterine contractions. When contractions are inadequate, the standard intervention is intravenous oxytocin. However, prolonged or high-dose oxytocin administration can lead to receptor desensitization, reducing its effectiveness and increasing the risk of postpartum hemorrhage.

Calcium plays a key role in myometrial contractility by facilitating calcium influx through L-type channels in myometrial cells, which triggers intracellular calcium release and action potentials. During labor, upregulation of calcium channels enhances the uterus's responsiveness to contractile stimuli. Elevated serum calcium levels have been associated with stronger and more effective contractions.

Adjunctive intravenous calcium administration with oxytocin has been shown to improve labor outcomes, including higher rates of vaginal delivery within 24 hours of induction and reduce blood loss in cesarean deliveries. However, the potential role of oral calcium supplementation in enhancing labor progression has not been evaluated in clinical trials. Given its physiological relevance, accessibility, and low-risk profile, oral calcium may represent a simple adjunct to improve labor efficiency and reduce cesarean rates.

This study aims to evaluate the impact of oral calcium carbonate supplementation during labor on uterine contractility and clinical outcomes. The investigators hypothesize that calcium carbonate administered intrapartum will enhance uterine contractions, resulting in higher vaginal delivery rates, shorter time to delivery, and reduced blood loss.

Being tested
Calcium carbonate
Keywords
calcium carbonate, labor, vaginal delivery, cesarean delivery
Medical subject headings
Obstetric Labor Complications, Dystocia

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Calcium carbonateDrug

    Also called TUMS

    2,000 mg PO calcium carbonate as a single dose

Study groups in NCT07056062
Study groupRoleWhat they receive
Standard of careNo interventionReceived no medications but monitored for the duration of the study
Calcium carbonateExperimental2,000 mg PO calcium carbonate as a single dose
Receives: Drug: Calcium carbonate

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Contraction Frequency

    Recording the number of contractions in a ten-minute period for 2 hours

    Measured: Two hours after receiving the study medication or, for control participants, two hours after enrollment.

  2. Uterine contraction strength

    Recording Montevideo units every 30 minutes for 2 hours

    Measured: Two hours after receiving the study medication or, for control participants, two hours after enrollment.

  3. Peak strength

    Recording the max pressure generated during a contraction using an intrauterine pressure catheter during the 2-hour study period

    Measured: Two hours after receiving the study medication or, for control participants, two hours after enrollment.

Secondary outcomes (6)

  1. Duration of the first stage of labor

    Record the length of the first stage of labor from 6 cm to 10 cm dilation

    Measured: Calculated at the time of delivery

  2. Duration of the second stage of labor

    Record the time from 10 cm to delivery of the baby

    Measured: Calculated at the time of delivery

  3. Mode of delivery

    Determine whether or not patient had a spontaneous vaginal bleeding, operative vaginal delivery, or cesarean delivery

    Measured: Calculated at the time of delivery

  4. Pitocin dose

    Record the maximum dose of Pitocin used during labor

    Measured: Calculated at the time of delivery

  5. Postpartum hemorrhage

    Determine which patients had a blood loss of greater than or equal to 1000 mL

    Measured: at the time of discharge (assessed up to 5 days)

  6. Neonatal outcomes

    Determine which babies were admitted to neonatal intensive care unit (NICU) and had a low 5- minute APGAR score

    Measured: at the time of discharge (assessed up to 5 days)

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted9 Jul 2025
  2. Study start30 Apr 2024
  3. Primary completion30 May 2025
  4. Study completion30 May 2025

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2/3
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Model description
Participants in the intervention group received a single oral dose of 2,000 mg calcium carbonate, consisting of four over-the-counter antacid tablets. This dose is well below the recommended daily maximum of 8,000 mg. The control group received no medication. Common side effects of calcium carbonate include constipation, bloating, and abdominal discomfort, while serious side effects such as hypercalcemia are rare.
Masking
None (open label)
Enrolment
89 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07056062
Sponsor's protocol ID
24-16
Status last verified
Jun 2025
First submitted
21 Jun 2025
Last updated
9 Jul 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Undecided: Study has already been completed, will analyze data first and then decide

Publications

  • Cai R, Chen L, Xing Y, Deng Y, Li J, Guo F, Liu L, Xie C, Yang J. RETRACTED: Oxytocin with calcium vs oxytocin for induction of labor in women with term premature rupture of membranes: a randomized controlled trial. Am J Obstet Gynecol MFM. 2024 Nov;6(11):101502. doi: 10.1016/j.ajogmf.2024.101502. Epub 2024 Sep 20.

    PubMed 39307241

  • Ansari JR, Yarmosh A, Michel G, Lyell D, Hedlin H, Cornfield DN, Carvalho B, Bateman BT. Intravenous Calcium to Decrease Blood Loss During Intrapartum Cesarean Delivery: A Randomized Controlled Trial. Obstet Gynecol. 2024 Jan 1;143(1):104-112. doi: 10.1097/AOG.0000000000005441. Epub 2023 Nov 3.

    PubMed 37917943

  • Papandreou L, Chasiotis G, Seferiadis K, Thanasoulias NC, Dousias V, Tsanadis G, Stefos T. Calcium levels during the initiation of labor. Eur J Obstet Gynecol Reprod Biol. 2004 Jul 15;115(1):17-22. doi: 10.1016/j.ejogrb.2003.11.032.

    PubMed 15223159

  • Pehlivanoglu B, Bayrak S, Dogan M. A close look at the contraction and relaxation of the myometrium; the role of calcium. J Turk Ger Gynecol Assoc. 2013 Dec 1;14(4):230-4. doi: 10.5152/jtgga.2013.67763. eCollection 2013.

    PubMed 24592112

  • Wray S, Jones K, Kupittayanant S, Li Y, Matthew A, Monir-Bishty E, Noble K, Pierce SJ, Quenby S, Shmygol AV. Calcium signaling and uterine contractility. J Soc Gynecol Investig. 2003 Jul;10(5):252-64. doi: 10.1016/s1071-5576(03)00089-3.

    PubMed 12853086

  • Obstetric care consensus no. 1: safe prevention of the primary cesarean delivery. Obstet Gynecol. 2014 Mar;123(3):693-711. doi: 10.1097/01.AOG.0000444441.04111.1d.

    PubMed 24553167

  • Bui TM, Nelson M, Rehman R, Stowe Ii RJ, Roloff KA, Valenzuela GJ. Effect of oral calcium carbonate on uterine contractility: a pilot randomised controlled trial. J Obstet Gynaecol. 2026 Dec;46(1):2697258. doi: 10.1080/01443615.2026.2697258. Epub 2026 Jul 21.

    PubMed 42480078

Questions about this trial

What is this clinical trial studying?

A Phase 2/3 study testing Calcium carbonate in people with Uterine Contraction and Labor Complication, run by Arrowhead Regional Medical Center at 1 site in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 14 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 9 Jul 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Contraction Frequency (time frame: Two hours after receiving the study medication or, for control participants, two hours after enrollment.). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07056062, which also lists 7 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 9 Jul 2025.

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