Arm Position and Blood Pressure Measurement Accuracy During Pregnancy

Overview

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, allowing each participant to serve as her own control. Participants will be enrolled in trimester-specific cohorts, and results will be analyzed separately for each trimester of pregnancy. 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.

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. The study consists of three separate prospective randomized crossover trials, each conducted within a specific trimester of pregnancy (first, second, and third trimesters). 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. The order of arm positions is randomized for each participant using a computerized randomization system, allowing each participant to serve as her own control. 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 independently for each trimester cohort, 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.