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Oral sodium hydrogen carbonate versus placebo to reduce assisted delivery in nulliparous women with prolonged labour

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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on women who are having their first baby and who develop Prolonged labour, a condition where labor lasts longer than expected and can increase the chance of needing help to deliver the baby. The trial tests whether an oral solution of Sodium hydrogen carbonate can reduce the need for an emergency caesarean section or an instrumental vaginal birth compared with a placebo, and the purpose of the study is to compare the benefits and harms of the bicarbonate treatment with the placebo.

Participants are randomly assigned to receive either the bicarbonate solution or the placebo during labor and are followed through delivery. Researchers will record whether delivery required the defined assisted methods and will also note if the newborn needs to stay in a neonatal intensive care unit within the first day, as well as the mother’s reported birth experience using the Childbirth Experience Questionnaire. The trial continues only for the duration of labor and the immediate postpartum period, after which the collected data are analyzed.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline information

    After you agree to join the trial, basic health information and details about your pregnancy are recorded.

    This information is used to confirm that you meet the study criteria for nulliparous women with prolonged labour.

  2. Step 2

    Random assignment to study medication

    You will be randomly assigned to receive either the test medication samarin or a placebo.

    The assignment is done by the study team and you will not know which one you receive.

  3. Step 3

    Receiving the oral medication

    The medication is provided as an oral solution.

    If you are assigned to the test group, the solution contains 16 g of sodium hydrogen carbonate (also known as bicarbonate).

    If you are assigned to the placebo group, the solution contains only inactive ingredients such as glucose, sodium chloride, silica, and a lemon‑peach flavoring.

  4. Step 4

    Taking the medication during labour

    When prolonged labour is diagnosed, you will be instructed to take the assigned oral solution.

    The dose is a single administration of the 16 g solution, taken by mouth as directed by the clinical staff.

  5. Step 5

    Monitoring during delivery

    Your labour progress and any need for assisted delivery will be monitored.

    Assisted delivery includes an emergency caesarean section or an instrumental vaginal birth.

  6. Step 6

    Post‑delivery assessment

    After birth, the health of the newborn is checked, including whether the child is admitted to a neonatal intensive care unit within the first 24 hours.

    You will be asked to complete a questionnaire about your birth experience.

Who can join the trial?

9 criteria

  • Age 18 years or older
  • Can speak Danish or English
  • Pregnant with a single baby (not twins or multiples)
  • Baby positioned head‑first (cephalic presentation)
  • Pregnancy between 35 weeks and 41 weeks + 6 days (gestational age) when labour begins
  • Normal baby heart rate (fetal heart rate) recorded within the 20 minutes before joining the study
  • Labour started on its own (spontaneous onset) or started without medication using a balloon catheter or by breaking the water (non‑medical induced labour)
  • In the active first stage of labour: cervix opened at least 4 cm but less than 10 cm and having regular painful contractions (cervical dilatation and regular painful contractions)
  • Diagnosed with prolonged labour according to Danish guidelines

Who cannot join the trial?

7 criteria

  • Having a serious kidney (renal) or heart problem, which the doctors will review for each person.
  • Having a serious pregnancy‑related problem (obstetric complication) that the doctors consider a risk.
  • Being suspected of an infection, such as having a fever of 38.5 °C (101.3 °F) or higher if you have an epidural, or 38 °C (100.4 °F) or higher without an epidural, or if you have started broad‑spectrum antibiotics (medicines that treat many kinds of bacteria).
  • Receiving oxytocin to speed up or strengthen labor (called oxytocin augmentation) at the time you would be entered into the study.
  • Having a known allergy or intolerance to sodium bicarbonate (the chemical also known as baking soda).
  • Having taken sodium bicarbonate during active labor before being entered into the study.
  • Currently taking any of the following medicines: gabapentin (used for nerve pain), tetracycline (an antibiotic), or ketoconazole (an antifungal medication).
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Investigated drugs

Samarin is an oral solution that contains sodium hydrogen carbonate, a type of antacid. In this study it is given to women who are in the early stages of a long labor to see if it can lower the chance that they will need an assisted delivery, such as an emergency C‑section or the use of forceps or a vacuum. The medicine is taken by mouth and works by neutralizing acid in the stomach, which researchers think might influence how the uterus contracts during labor.

What is already known about the treatment

Sodium hydrogen carbonate (Samarin) - This medication is supplied as an oral solution that is taken by drinking the liquid. It is an established antacid that is widely available over the counter and well described in medical literature. It is mainly used to neutralize excess stomach acid and can also be given to correct mild metabolic acidosis, and in this trial it is being tested to see if it helps reduce assisted delivery during prolonged labour. The drug works by providing bicarbonate ions that combine with hydrogen ions in the stomach to form carbon dioxide and water, thereby raising the pH; it belongs to the antacid class of sodium bicarbonate preparations.

Investigated diseases

Prolonged labor - Prolonged labor is a condition in which the birth process lasts longer than the typical duration for a first‑time mother, often extending beyond 20 hours of active labor. It starts with regular uterine contractions that fail to open the cervix efficiently. Over time the cervical dilation progresses very slowly despite the continued effort of the uterus. The baby may remain high in the birth canal and does not move down as expected. As the labor continues, uterine strength can diminish, leading to weaker contractions. The prolonged nature of the process may eventually require assistance to complete the birth.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525682-45-00Estimated enrolment1 520 patientsSponsorRegion Hovedstaden

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