Arm Position and Blood Pressure Measurement Accuracy During Pregnancy

Arm Position and Blood Pressure Measurement Accuracy in Pregnancy: A Randomized Controlled Trial

Accurate blood pressure measurement is essential during pregnancy, as blood pressure readings guide clinical decisions related to the diagnosis and management of hypertensive disorders of pregnancy. Clinical guidelines recommend measuring blood pressure with the arm supported at heart level; however, in routine practice, blood pressure is often measured with the arm in non-standard positions.

This study aims to evaluate how different arm positions affect blood pressure measurements in pregnant women. Pregnant women attending a high-risk pregnancy clinic will undergo blood pressure measurements with the arm placed in several commonly used positions, including supported at heart level, supported on the lap, and unsupported at the side. Each participant will have multiple measurements taken during a single clinic visit.

The study is designed as a randomized crossover trial with stratification by trimester and chronic hypertension status, allowing each participant to serve as her own control. Participants will be enrolled across all three trimesters of pregnancy, and results will be analyzed separately for each trimester. The primary outcome is the difference in systolic and diastolic blood pressure measurements between arm positions.

The findings of this study may help improve the accuracy of blood pressure measurement during pregnancy and inform clinical practice regarding optimal measurement techniques.

Study Overview

• Status: Recruiting
• Conditions: Pregnancy; Hypertensive Disorder of Pregnancy; Blood Pressure Measurement in Pregnancy
• Intervention / Treatment: Other: Arm Supported at Heart Level; Other: Arm Supported on Lap; Other: Arm Unsupported at Side

Detailed Description

Blood pressure measurement is a routine and essential component of prenatal care and plays a central role in the diagnosis and management of hypertensive disorders of pregnancy. International and national guidelines recommend measuring blood pressure with the patient seated, after a period of rest, and with the arm supported at heart level. Despite these recommendations, blood pressure in clinical practice is frequently measured with the arm placed in non-standard positions, which may lead to inaccurate readings and potential misclassification of blood pressure status.

This study is designed to assess the effect of arm position on blood pressure measurements in pregnant women. This is a single prospective randomized crossover trial conducted across all three trimesters of pregnancy. Randomization of arm position order is performed using a computerized block randomization system with stratification by trimester (first, second, third) and chronic hypertension status.

Participants are enrolled during routine visits to a high-risk pregnancy clinic and are assigned to a trimester-specific cohort based on gestational age at the time of enrollment. During a single clinic visit, each participant undergoes multiple blood pressure measurements with the arm positioned in several commonly used positions: supported on a desk at heart level, supported on the lap, and unsupported at the side. To account for natural variability in blood pressure measurements, an additional set of measurements with the arm supported at heart level is obtained. Each participant serves as her own control within the randomized crossover design.

Blood pressure measurements are performed by trained nursing staff using a clinically approved automated blood pressure device, following a standardized measurement protocol. All measurements are obtained after a resting period and while the participant is seated comfortably.

Participants are recruited across all three trimesters, and analyses are conducted separately by trimester. The primary outcome is the difference in systolic and diastolic blood pressure measurements between arm positions. Secondary analyses evaluate the magnitude and pattern of blood pressure differences across gestational ages and relevant clinical subgroups.

This study involves minimal risk and does not alter standard clinical care. The results are intended to improve understanding of how arm positioning influences blood pressure measurements during pregnancy and to inform best practices for accurate blood pressure assessment in prenatal care.

• Study Type: Interventional
• Enrollment (Estimated): 300
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Michal Axelrod, MD MPH; Phone Number: +97235302697; Email: michalaxelrod2805@gmail.com

Study Locations

• Israel
  • Ramat Gan, Israel, 5265217
    • Recruiting
    • Sheba Medical Center
    • Contact: Michal Axelrod, MD MPH; Phone Number: +97235302697; Email: michalaxelrod2805@gmail.com
    • Principal Investigator: Michal Axelrod, MD MPH

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Pregnant women aged 18 to 55 years
• Singleton or multiple viable intrauterine pregnancy
• Gestational age corresponding to first, second, or third trimester at the time of enrollment
• Ability to sit upright comfortably for the duration of blood pressure measurements
• Ability to understand the study procedures and provide written informed consent

Exclusion Criteria:

• Preexisting significant cardiac disease (e.g., arrhythmias, congenital heart disease, severe valvular disease)
• Chronic kidney disease defined as serum creatinine ≥1.5 mg/dL at enrollment
• Significant upper limb or shoulder conditions that may affect arm positioning or blood pressure measurement (e.g., lymphedema, fractures, prior surgery, arteriovenous fistula)
• Neurological or musculoskeletal conditions preventing proper positioning
• Severe preeclampsia, eclampsia, or other acute medical conditions requiring immediate intervention
• Major fetal anomaly
• Intrauterine fetal demise

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Arm Supported at Heart Level; Blood pressure measurements are obtained with the arm supported at heart level while the participant is seated.	Other: Arm Supported at Heart Level; Blood pressure measurements are obtained with the arm supported at heart level while the participant is seated.
Experimental: Arm Supported on Lap; Blood pressure measurements are obtained with the arm supported on the participant's lap while seated.	Other: Arm Supported on Lap; Blood pressure measurements are obtained with the arm supported on the participant's lap while seated.
Experimental: Arm Unsupported at Side; Blood pressure measurements are obtained with the arm unsupported at the participant's side while seated.	Other: Arm Unsupported at Side; Blood pressure measurements are obtained with the arm unsupported at the participant's side while seated.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in Systolic and Diastolic Blood Pressure Between Arm Positions	The within-participant difference in mean systolic and diastolic blood pressure measurements obtained with the arm supported at heart level, supported on the lap, and unsupported at the side. Blood pressure values are calculated as the mean of triplicate measurements for each arm position.	At the study visit (single study visit on the day 1 of enrollment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Magnitude of Blood Pressure Differences Between Arm Positions	The absolute difference in mean systolic and diastolic blood pressure measurements between each pair of arm positions (supported at heart level, supported on the lap, unsupported at the side), calculated within each participant.	At the study visit (single study visit on the day 1 of enrollment)
Variation in Blood Pressure Differences Across Gestational Age	Comparison of within-participant differences in systolic and diastolic blood pressure between arm positions across trimester-specific cohorts of pregnancy.	At the study visit (single study visit on the day 1 of enrollment)
Effect of Arm Position on Blood Pressure by Chronic Hypertension Status	Comparison of within-participant differences in systolic and diastolic blood pressure between arm positions among participants with and without preexisting chronic hypertension.	At the study visit (single study visit on the day 1 of enrollment)
Comparison of Systolic Versus Diastolic Blood Pressure Sensitivity to Arm Position	Assessment of differences in the magnitude of arm position-related variation between systolic and diastolic blood pressure measurements within participants.	At the study visit (single study visit on the day 1 of enrollment)
Blood Pressure Differences by Singleton Versus Multiple Pregnancy	Comparison of within-participant differences in systolic and diastolic blood pressure between arm positions in singleton and multiple pregnancies.	At the study visit (single study visit on the day 1 of enrollment)

Collaborators and Investigators

• Sponsor: Sheba Medical Center

Publications and helpful links

General Publications

• Liu H, Zhao D, Sabit A, Pathiravasan CH, Ishigami J, Charleston J, Miller ER 3rd, Matsushita K, Appel LJ, Brady TM. Arm Position and Blood Pressure Readings: The ARMS Crossover Randomized Clinical Trial. JAMA Intern Med. 2024 Dec 1;184(12):1436-1442. doi: 10.1001/jamainternmed.2024.5213.

Study record dates

Study Major Dates

• Study Start (Actual): April 12, 2026
• Primary Completion (Estimated): September 1, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: February 3, 2026
• First Submitted That Met QC Criteria: February 11, 2026
• First Posted (Actual): February 12, 2026

Study Record Updates

• Last Update Posted (Actual): April 16, 2026
• Last Update Submitted That Met QC Criteria: April 13, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Pregnancy; Prenatal Care; Hypertensive Disorders of Pregnancy; Blood Pressure Accuracy; Blood Pressure Measurement; Randomized Crossover Trial; Arm Position
• Additional Relevant MeSH Terms: Infections; Toxemia
• Other Study ID Numbers: 2177-25-SMC (Other Identifier: Sheba Medical Center IRB)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Individual participant data sharing plans have not yet been determined. Any future data sharing will be subject to institutional policies, ethical approvals, and data protection requirements.

Drug and device information, study documents

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