Blood Pressure Measurement in Pregnancy – Interarm Differences and The Necessity of Multiple Consecutive Measurements

Abstract

Objective: To investigate multiple blood pressure measurements and interarm differences in a pregnant population. Method: Pregnant women attending routine antenatal ultrasound scans in gestational weeks 11-13 or week 20 had three consecutive blood pressure measurements on each arm conducted according to international guidelines. Mean and mean difference between the 1st measurement (BP-A) and 2nd + 3rd measurements combined (BP-B) as well as between right and left arm, respectively, were calculated and compared by paired t-test. Bland-Altman plots illustrate means and mean-differences of systolic and diastolic pressure between BP-A and BP-B. Results: One-hundred women were included. Mean systolic, diastolic and arterial blood pressure for BP-A were 112.1 mmHg, 70.6 mmHg and 84.4 mmHg, respectively, while mean BP-B were 109.8 mmHg, 69.2 mmHg and 82.8 mmHg. Mean differences in systolic, diastolic and mean arterial pressure (MAP) between BP-A and BP-B were 2.5 mmHg (P<0.001, 95% Confidence interval (CI) 1.7;3.2), 1.5 mmHg (P<0.001, 95% CI 1.0;2.0) and 1.8 mmHg (P<0.001, 95% CI 1.4;2.2). Mean interarm differences in systolic, diastolic and MAP were 3.1 mmHg (P<0.001, 95% CI 1.9;4.3), 0.75 mmHg (P=0.019, 95%CI 0.1;1.4) and 2.4 mmHg (P=0.01, 95% CI 0.6;4.2). Conclusion: In pregnancy, the first blood pressure measurement of three consecutive is significantly higher than the following two. Blood pressure on the right arm is significantly higher compared to the left arm. International guidelines on blood pressure measurements should apply to pregnant women.