Early Labor Pre-Marking for Epidural Analgesia: Ultrasound vs Manual Palpation

June 21, 2026 updated by: An Vu Nguyen, MD, University Medical Center Ho Chi Minh City (UMC)

Efficacy of Ultrasound-Guided Versus Landmark-Based Epidural Labor Analgesia: A Randomized Clinical Trial.

The goal of this clinical trial is to learn if finding and marking the best spot on the back early in labor helps doctors perform epidural pain relief more successfully in pregnant women. Usually, epidural pain relief is requested when labor pain is already severe, which makes it hard for women to hold still. This makes it difficult to find the right needle spot, leading to more needle attempts

The main questions this study aims to answer are:

  • Does using ultrasound to mark the back early in labor (before severe pain starts) help the doctor place the needle correctly on first try without adjusting it?
  • Does this early marking method lower the number of needle attempts and the time it takes to finish the procedure? Researchers will compare marking the back using an ultrasound machine to the standard method of feeling the spine with hands. Both methods will be done early in the waiting room to avoid the challenges caused by severe pain. Importantly, neither the pregnant women nor the doctors performing the epidural will know which marking method was used. This design prevents personal beliefs or expectations from affecting the procedure, making the study results objective and trustworthy.

Participants will, if consented and participated in the study:

  • Have their lower back examined and marked by a doctor early in labor using either an ultrasound machine or the doctor's hands.
  • Receive an epidural pain relief in the delivery room when they request it. This will be done by a different doctor who does not know how the back was marked.
  • Answer short questions about their pain level and how happy they are with the procedure.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

  1. Background Epidural analgesia is a widely accepted and highly effective method for managing labor pain. Traditionally, anesthesiologists identify the epidural insertion site by manually palpating anatomical landmarks. However, this conventional approach can be challenging and imprecise for many parturients. Factors such as soft tissue edema, exaggerated lumbar curvature during pregnancy, and rising obesity rates can obscure bony landmarks. Furthermore, frequent and painful uterine contractions during active labor often hinder the patient from maintaining the ideal flexed posture required for the procedure. These clinical challenges can result in multiple needle insertions, frequent redirections, prolonged procedure times, and an increased risk of patient discomfort or procedural complications.

    Pre-procedural spinal ultrasound has emerged as a valuable tool to address these limitations. By visualizing the anatomy in advance, clinicians can accurately identify the appropriate intervertebral space, locate the midline, determine the optimal needle insertion point and angle, and measure the precise distance from the skin to the epidural space. While prior research indicates that ultrasound guidance reduces technical difficulty, minimizes needle passes, and enhances first-attempt success rates, many of these studies lacked rigorous blinding or involved the same clinician performing both the ultrasound and the epidural placement, introducing potential observer bias. Additionally, in Vietnam, there is a lack of high-quality interventional research comparing ultrasound-assisted and traditional palpation techniques using standardized outcome measures.

    Therefore, this randomized, double-blind clinical trial aims to evaluate the efficacy of ultrasound-assisted marking versus conventional palpation for labor epidural analgesia. We hypothesize that pre-procedural spinal ultrasound guidance significantly improves the first-attempt success rate without requiring needle redirection when compared to the traditional technique. The results of this study aim to optimize clinical practice by promoting routine use of pre-procedural ultrasound to enhance safety, efficacy and the overall childbirth experience. A key feature of this study is performing ultrasound assessment early in labor, prior to the onset of severe pain or a request for analgesia. This timing allows the parturient to remain comfortable, alert, and highly cooperative, ensuring precise marking. Once active labor necessitates epidural analgesia, the attending physician anesthesiologist can rely on the pre-marked site, streamlining the procedure and reducing patient wait times and distress

  2. Study Objectives

    • Objective The objective of this study is to evaluate the effectiveness of neuraxial ultrasound compared with the conventional anatomical landmark palpation technique for epidural analgesia during labor.
    • Primary Objective: To compare the success rate of the first needle pass without any needle redirection between the ultrasound-assisted group and the landmark-based group.
    • Secondary Objectives: To compare other procedural characteristics, including the overall success rate of the first skin puncture, the total number of skin punctures, the number of needle redirections, the total procedure time, and the incidence of procedural complications (e.g., paresthesia, vascular puncture, dural puncture).
  3. Study Design and Methodology: This is a randomized, double-blind, controlled clinical trial conducted at the Obstetrics Department of the University Medical Center Ho Chi Minh City. Parturients are randomly assigned (in a 1:1 ratio using block randomization) to either the Ultrasound Group or the Landmark Group.

  4. Detailed Intervention Workflow: The study protocol is distinctly divided into two phases managed by different personnel to ensure strict blinding:

    Phase 1: Pre-procedural Assessment and Marking (Labor Room) Parturients are positioned in the lateral decubitus position (knees flexed to the abdomen, neck flexed) to maximize the opening of the intervertebral spaces. The first investigator (an anesthesiologist experienced in neuraxial ultrasound) opens the sealed randomization envelope and performs the assessment:

    • For the Ultrasound Group: The investigator uses an ultrasound machine with a 2-5 MHz curved transducer. The L3-L4 intervertebral space is identified via the paramedian sagittal oblique view (counting upwards from the sacrum). The probe is then rotated 90 degrees to the transverse interspinous view to identify the exact midline and the optimal posterior complex. The optimal needle entry point is marked on the skin using a surgical marker, and the skin-to-epidural depth is measured via the ultrasound image.
    • For the Landmark Group: The investigator manually palpates the anatomical landmarks to identify the L3-L4 intervertebral space and marks the midline insertion site on the skin with a surgical marker. Subsequently, the investigator uses ultrasound strictly to measure the skin-to-epidural depth at this pre-marked site for data collection purposes only, without altering the physical mark.

    Phase 2: Epidural Placement (Delivery Room) Once marked, the parturient is transferred to the delivery room for the epidural procedure.

    • A second anesthesiologist (the proceduralist), completely blinded to the group allocation, performs the epidural placement.
    • The proceduralist is required to insert the Tuohy needle exactly at the pre-marked site on the skin. To maximize patient safety, the proceduralist is informed of the ultrasound-measured skin-to-dura depth before initiating the puncture.
    • Procedural Rules: If the epidural space cannot be accessed, the proceduralist is allowed a maximum of 5 needle redirections (defined as changing the needle trajectory without completely withdrawing the needle tip from the skin). If the space is still not found after 5 redirections, the physician must completely withdraw the Tuohy needle from the skin, manually re-identify the anatomical landmarks, and perform a second skin puncture at a newly determined site.
    • Failure Criteria: The procedure is classified as a technical failure if the proceduralist cannot locate the epidural space after 3 complete skin punctures at different locations.
  5. Data Collection: All procedural data, timings, and clinical outcomes are meticulously recorded by an independent anesthetic nurse present in the delivery room, who is also completely blinded to the randomization.

Study Type

Interventional

Enrollment (Estimated)

100

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: An Vu Nguyen, MD, MSc
  • Phone Number: 6447 +84826027842
  • Email: an.nv1@umc.edu.vn

Study Contact Backup

Study Locations

  • Vietnam
    • Ho Chi Minh
      • Ho Chi Minh City, Ho Chi Minh, Vietnam, 700000
        • Recruiting
        • University Medical Center Ho Chi Minh City
        • Contact:
        • Contact:
        • Principal Investigator:
          • An Vũ Nguyễn, MD, MSc
        • Sub-Investigator:
          • Nhựt Minh Nguyễn, MD, MSc
        • Sub-Investigator:
          • Tín Trọng Võ, MD, 1st Degree Specialist
        • Sub-Investigator:
          • Như Lê Quỳnh Dương, MD, 1st Degree Specialist
        • Sub-Investigator:
          • Thiểu Thị Bích Huỳnh, Nurse Anesthetist
        • Sub-Investigator:
          • Phương Ngọc Thanh Vũ, Nurse Anesthetist
        • Sub-Investigator:
          • Uyên Thị Ngọc Trịnh, Nurse Anesthetist

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Parturients aged 18 years and older, gestational age is 37 weeks or older.
  • Actively requesting epidural analgesia for labor pain management without any contraindication to the procedure.

Exclusion Criteria:

  • Parturients with spinal abnormalities or a history of spinal surgery.
  • Inability to visualize epidural landmarks under ultrasound imaging.
  • Parturients experiencing severe pain requiring immediate, emergent labor analgesia.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Ultrasound group
Participants in this arm will undergo pre-procedural spinal ultrasound while on the left lateral decubitus position. The ultrasound is used to identify the L3-L4 interspace, the midline, and the optimal needle insertion point.
Procedure: Preprocedural Spinal Ultrasound
A curvilinear probe is applied to the lower back in a transverse orientation. The vertebral midline is marked after identifying a symmetrical image in the transverse spinous process view. The probe is then oriented to obtain a paramedian sagittal laminar view. After locating the sacrum and lumbosacral junction, the probe is moved cephalad to identify and mark the L3 and L4 laminae. The probe is rotated back to a transverse view to systematically assess the lumbar interlaminar spaces, using the posterior complex (ligamentum flavum, epidural space, and posterior dura) and the anterior complex (anterior dura, posterior longitudinal ligament, and posterior vertebral body) as key landmarks. Markings are done with pen at four midpoints of the probe's edges in the L3-L4 space with the largest acoustic window. The intersection of horizontal and vertical lines drawn from these marks designates the needle insertion point.
Active Comparator: Landmark Group
Participants in this arm will undergo manual palpation of surface bony landmarks of L3-L4 interspace while on the left lateral decubitus position. This conventional approach determines the needle insertion point without relying on ultrasound guidance.
Procedure: Conventional Landmark Palpation
The anesthesiologist manually palpates anatomical landmarks to identify L3-L4 interspace and marks the midline insertion site. An ultrasound probe is then placed over this marked site only to measure skin-to-epidural depth for data collection purposes. These measurements are recorded but are not used to adjust or alter the marked insertion point.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
First-pass success
Time Frame: Periprocedural
Yes/No variable. First-pass success was defined as the successful identification of the epidural space during the initial forward advancement of the needle, without any needle redirection or withdrawal
Periprocedural

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
First-attempt success
Time Frame: Periprocedural
Yes/No variable. First-attempt success was defined as the successful identification of the epidural space achieved with only a single skin puncture
Periprocedural
Number of needle redirections
Time Frame: Periprocedural
A needle redirection was defined as any partial withdrawal of the needle followed by a change in its advancement angle without the needle tip exiting the skin surface.
Periprocedural
Number of needle attempts
Time Frame: Periprocedural
A attempt was defined as a new skin puncture after the needle had been completely withdrawn.
Periprocedural
Procedure time
Time Frame: Periprocedural
Measured in seconds. Time from the moment inserts the Touhy needle at the marked position to final catheter fixation.
Periprocedural
Paresthesia
Time Frame: Periprocedural
Yes/No variable. Paresthesia was defined as any abnormal sensation (electric shock-like, tingling, or numbness) reported by the patient during needle insertion or catheter insertion.
Periprocedural
Vascular puncture
Time Frame: Periprocedural
Yes/No variable. Vascular puncture was defined as the presence of blood in the catheter or flashback in the needle.
Periprocedural
Dural puncture
Time Frame: Periprocedural
Yes/No variable. Presence of cerebrospinal fluid (CSF) in the Tuohy needle or upon catheter aspiration
Periprocedural
Adequate analgesia
Time Frame: 1 hour post-procedure
Yes/No variable. VAS less than 3 at one hour post procedurally.
1 hour post-procedure
Maternal satisfaction
Time Frame: 2 hours postpartum
Patient satisfaction of the procedure was measured on a 0-10 Visual Analog Scale (VAS), where 0 represented 'completely dissatisfied' and 10 represented 'completely satisfied'.
2 hours postpartum
Procedure failure
Time Frame: Periprocedural
Yes/No variable. Procedure failure was defined as the inability to identify the epidural space after attempting at three different skin puncture sites
Periprocedural
Change of intervertebral space
Time Frame: Periprocedural
Yes/No variable. A change of intervertebral space was defined as the complete withdrawal of the needle from the initially selected spinal level and re-insertion at a different level.
Periprocedural

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University Medical Center Ho Chi Minh City (UMC)

Investigators

  • Principal Investigator: An Vu Nguyen, MD, MSc, University Medical Center Ho Chi Minh City

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 1, 2026

Primary Completion (Estimated)

August 30, 2026

Study Completion (Estimated)

August 30, 2026

Study Registration Dates

First Submitted

June 21, 2026

First Submitted That Met QC Criteria

June 21, 2026

First Posted (Actual)

June 25, 2026

Study Record Updates

Last Update Posted (Actual)

June 25, 2026

Last Update Submitted That Met QC Criteria

June 21, 2026

Last Verified

June 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 104/GCN-HDDD

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

To protect the privacy and confidentiality of the participants in accordance with institutional and national guidelines

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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