Recovery Rate From Category II to Category I EFM Tracings in Pregnant Women Receiving Bolus vs Continuous Intravenous Fluid Administration (IUR-RCT)

This randomized trial compared a normal saline bolus regimen with continuous normal saline infusion. The participants were low-risk pregnant women at term with Category II fetal heart rate tracings. Both groups were prescribed 1,000 mL of normal saline through the same volumetric infusion pump. The bolus group received 500 mL at 1,000 mL/h during the first 30 minutes, followed by 150 mL/h. The continuous group received 150 mL/h throughout. The primary outcome was first recovery from Category II to Category I within 30 minutes. Both groups also received standard intrauterine resuscitation. Fetal heart rate tracings were assessed at 30, 60, and 120 minutes.

Study Overview

• Status: Completed
• Conditions: Category II Fetal Heart Rate Tracing
• Intervention / Treatment: Drug: Normal saline bolus infusion; Drug: Continuous normal saline infusion

Detailed Description

Intravenous fluid is a component of intrauterine resuscitation for Category II fetal heart rate tracings. No randomized trial had directly compared bolus and continuous intravenous fluid administration.

Both arms were prescribed 1,000 mL of normal saline through a 21-gauge cannula and the same volumetric infusion pump. The bolus group received 500 mL at 1,000 mL/h during the first 30 minutes. The remaining 500 mL was then administered at 150 mL/h. The continuous group received 150 mL/h throughout. Programmed delivery by 30 minutes was approximately 500 mL in the bolus group and 75 mL in the continuous group. Resuscitation continued until the attending declared Category I recovery or until 120 minutes.

Both groups received standard intrauterine resuscitation. This included left lateral positioning, oxytocin discontinuation where applicable, and oxygen at 10 L/min through a face mask.

The primary outcome was first recovery from Category II to Category I within 30 minutes. First Category I recovery was an absorbing endpoint. A later observed Category II classification did not reverse recovered endpoint status. The participant and attending outcome assessor were masked to allocation. Two masked reviewers independently re-adjudicated the fetal heart rate classifications.

A trained operator measured the inferior vena cava collapsibility index and umbilical artery Doppler pulsatility index at baseline and 30 minutes. The primary analysis used Fisher's exact test, risk difference, relative risk, and number needed to treat.

• Study Type: Interventional
• Enrollment (Actual): 60
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Thailand
  • Changwat Chon Buri
    • Si Racha, Changwat Chon Buri, Thailand, 20110
      • Queen Savang Vadhana Memorial Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Singleton pregnancy
• Thai nationality
• Gestational age of 37 weeks or more
• Maternal age from 20 to 35 years
• Cephalic presentation
• Category II electronic fetal monitoring tracing during labor

Exclusion Criteria:

• Pre-existing cardiac, pulmonary, thyroid, or overt diabetic disease
• Pre-eclampsia or gestational diabetes
• Suspected fetal structural anomaly, growth restriction, arrhythmia, or chromosomal abnormality
• Recent magnesium sulfate or opioid analgesia
• Oligohydramnios

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Group A: Bolus group; Participants were prescribed 1,000 mL of normal saline through a 21-gauge cannula and the same volumetric infusion pump. The first 500 mL was administered at 1,000 mL/h during the first 30 minutes. The remaining 500 mL was then administered at 150 mL/h. Resuscitation continued until the attending declared Category I recovery or until 120 minutes.	Drug: Normal saline bolus infusion; Participants were prescribed 1,000 mL of normal saline through a 21-gauge cannula and the same volumetric infusion pump. The first 500 mL was administered at 1,000 mL/h during the first 30 minutes. The remaining 500 mL was then administered at 150 mL/h. The intervention continued until the attending declared Category I recovery or until 120 minutes.
Experimental: Group B: Continuous group; Participants were prescribed 1,000 mL of normal saline through a 21-gauge cannula and the same volumetric infusion pump. Normal saline was administered at 150 mL/h throughout. Resuscitation continued until the attending declared Category I recovery or until 120 minutes.	Drug: Continuous normal saline infusion; Participants were prescribed 1,000 mL of normal saline through a 21-gauge cannula and the same volumetric infusion pump. Normal saline was administered continuously at 150 mL/h throughout. The intervention continued until the attending declared Category I recovery or until 120 minutes.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
First recovery from Category II to Category I EFM tracing within 30 minutes	Proportion of participants with first recovery from Category II to Category I electronic fetal monitoring tracing within 30 minutes of intervention initiation, classified using the NICHD three-tier system. First Category I recovery was an absorbing endpoint. A later observed Category II classification did not reverse recovered endpoint status. Non-recovery was persistent Category II or progression to Category III. Classification was performed in real time by the masked attending outcome assessor.	30 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mode of delivery	Route of delivery classified as vaginal delivery or caesarean section.	At delivery
Neonatal Intensive Care Unit (NICU) admission	Proportion of neonates admitted to the neonatal intensive care unit following delivery.	Within 24 hours of delivery
Apgar score at 1 minute	Proportion of neonates with 1-minute Apgar score below 7	1 minute after delivery
Apgar score at 5 minutes	Proportion of neonates with 5-minute Apgar score below 7	5 minutes after delivery
First recovery from Category II to Category I EFM tracing within 60 minutes	Cumulative proportion of participants with first recovery from Category II to Category I electronic fetal monitoring tracing within 60 minutes of intervention initiation, classified using the NICHD three-tier system. First Category I recovery was an absorbing endpoint. A later observed Category II classification did not reverse recovered endpoint status. Non-recovery by 60 minutes was persistent Category II or progression to Category III.	60 minutes
First recovery from Category II to Category I EFM tracing within 120 minutes	Cumulative proportion of participants with first recovery from Category II to Category I electronic fetal monitoring tracing within 120 minutes of intervention initiation, classified using the NICHD three-tier system. First Category I recovery was an absorbing endpoint. A later observed Category II classification did not reverse recovered endpoint status. Non-recovery by 120 minutes was persistent Category II or progression to Category III.	120 minutes

Collaborators and Investigators

• Sponsor: Queen Savang Vadhana Memorial Hospital, Thailand

Publications and helpful links

General Publications

• 1. World Health Organization. WHO statement on caesarean section rates. WHO/RHR/15.02. Geneva: World Health Organization; 2015. 2. Royal Thai College of Obstetricians Gynaecologists. Position Statement on Caesarean Section (Revised Edition 2023). Bangkok: RTCOG; 2023. 3. Freeman RK, Garite TJ, Nageotte MP, Miller LA. Fetal Heart Rate Monitoring. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2012. 4. Abati I, Micaglio M, Giugni D, Seravalli V, Vannucci G, Di Tommaso M. Maternal oxygen administration during labor: a controversial practice. Children. 2023;10(8):1420. 5. Kearney L, Craswell A, Dick N, Massey D, Nugent R. Evidence-based guidelines for intrapartum maternal hydration assessment and management: a scoping review. Birth. 2024;51(2):253-63. 6. Simpson KR, James DC. Efficacy of intrauterine resuscitation techniques in improving fetal oxygen status during labor. Obstetrics & Gynecology. 2005;105(6):1362-8. 7. Reddy UM, Weiner SJ, Saade GR, Varner MW, Blackwell SC, Thorp JM, Jr. Intrapartum resuscitation interventions for category II fetal heart rate tracings and improvement to category I. Obstetrics & Gynecology. 2021;138(3):409-16. 8. American College of Obstetrician Gynecologists. Practice Bulletin No. 116: Management of intrapartum fetal heart rate tracings. Obstetrics & Gynecology. 2010;116(5):1232-40. 9. Kitsricharoenchai A, Sunsaneevithayakul P, Boriboonhirunsarn D. Success rate of intrauterine fetal resuscitation in NICHD category II abnormal fetal heart rate pattern. Thai Journal of Obstetrics and Gynaecology. 2021;29(3):159-68. 10. Hopewell S, Chan A-W, Collins GS, Hróbjartsson A, Moher D, Schulz KF, et al. CONSORT 2025 statement: updated guideline for reporting randomised trials. BMJ. 2025;389:e081123. 11. Hoffmann TC, Glasziou PP, Boutron I, Milne R, Perera R, Moher D, et al. Better reporting of interventions: template for intervention description and replication (TIDieR) checklist and guide. BMJ. 2014;348:g1687. 12. Manyara AM, Davies P, Stewa

Study record dates

Study Major Dates

• Study Start (Actual): December 10, 2025
• Primary Completion (Actual): March 27, 2026
• Study Completion (Actual): March 31, 2026

Study Registration Dates

• First Submitted: November 20, 2025
• First Submitted That Met QC Criteria: November 20, 2025
• First Posted (Actual): December 3, 2025

Study Record Updates

• Last Update Posted (Actual): August 17, 2026
• Last Update Submitted That Met QC Criteria: August 13, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: electronic fetal monitoring; bolus intravenous fluid administration; continuous intravenous fluid administration; Category II fetal heart rate tracing; intrauterine resuscitation
• Additional Relevant MeSH Terms: Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Fetal Distress
• Other Study ID Numbers: 013/2568

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Deidentified individual participant data that underlie the reported results may be available from the corresponding author. Direct identifiers will not be shared. Participant confidentiality and the Thailand Personal Data Protection Act B.E. 2562 (2019) will apply.
• IPD Sharing Time Frame: Requests will be considered after publication of the primary results. No fixed end date is planned.
• IPD Sharing Access Criteria: Qualified researchers must submit a written request to the corresponding author. The request must include a research proposal, requested variables, planned analyses, and evidence of ethics approval. Access requires institutional review board approval and a signed data use agreement. Approved data must remain secure and cannot be used to identify participants. Use must comply with the Thailand Personal Data Protection Act B.E. 2562 (2019).
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No