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Objective:Hypertensive disorders of pregnancy are leading causes of maternal and perinatal morbidity and mortality. Automated blood pressure (BP) measurements are being used in clinical practice; however, understanding of how oscillometric waveform vary between pregnant and non-pregnant individuals remains low.Design and Methods:Pregnant individuals over 20 weeks gestational age and healthy, non-pregnant women were recruited. Healthy, non-pregnant women (HNP) were matched to healthy pregnant women (HP), and pregnant women with a hypertensive disorder of pregnancy (HDP) by age (± 10 years), arm circumference (± 6 cm), and BMI at the time of BP measurement (± 13 kg/m2). There were seven individuals in each group for a total of 21 participants. BP measurements were done per the International Organization for Standardization (ISO) protocol using a custom-built oscillometric device as the test device and 2-observer mercury auscultation as the reference measurement. Four pairs of auscultatory measurements and four oscillometric measurements were obtained for each participant. Baseline demographics, auscultatory BP and BP derived from slope-based and fixed ratio algorithms were determined. Oscillometric waveform and envelope features were compared among groups.Results:In HNP, HP, and HDP groups respectively: mean age was 31.3 ± 4.8; 32.1 ± 3.6; 32.0 ± 4.4 years; arm circumference 31.9 ± 3.3; 32.3 ± 4.9; 34.0 ± 3.3 cm; BMI 26.8 ± 3.8; 32.0 ± 7.2; 32.4 ± 3.7 kg/m2; mean auscultatory BP (systolic/diastolic) 103.3 ± 11.1/66.5 ± 7.4; 110.6 ± 4.0/56.9 ± 6.5; 132.6 ± 19.0/83.9 ± 13.3 mmHg. HDP had significantly higher auscultatory systolic (P < 0.05) and diastolic (p < 0.01) BP than the other groups. The pregnant groups (HP, HDP) had significantly higher heart rate (p < 0.01); higher pulses (p < 0.05) in the oscillometric waveform (OMV); lower average width in the pulses (p < 0.01); higher pressure amplitude at which the OMW peaks (p < 0.05) with longer time to reach this maximum pressure amplitude (p < 0.05); greater area under the curve (p < 0.01). Compared to HNP, the HDP showed significantly skewed OMW to the right (p < 0.01); greater spread in the OMW envelope (p < 0.05) and lesser random variation in the OMW envelope (p < 0.01). A typical OMV with the 3 groups superimposed is demonstrated in Figure 1.Conclusion:Significant differences in the oscillometric waveform morphology and parameters were found in pregnancy and in hypertensive disorders of pregnancy compared to healthy controls. These results suggest that pregnancy-specific algorithms may be required to optimize accuracy for oscillometric BP measurement.Figure 1Healthy non-pregnant, healthy pregnant, and pregnant with a hypertensive disorder of pregnancy oscillometric waveforms superimposed.