Use of automated home blood pressure monitoring in pregnancy: Is it safe?

OBJECTIVE: The purpose of this study was to investigate the relationship between blood pressure that is measured with the automated blood pressure monitor, Omron HEM-705CP (Omron Corporation, Tokyo, Japan), and mercury sphygmomanometry in normotensive and preeclamptic pregnant women. STUDY DESIGN: Healthy pregnant women (n = 101 women) underwent mercury and home Omron HEM-705CP monitor blood pressure measurements at 10 to 14, 19 to 22, 27 to 30, and 35 to 37 weeks of gestation and 5 to 9 weeks after delivery. After routine mercury blood pressure recordings that were taken by midwives, women with preeclampsia (n = 45 women) measured their own blood pressure using an Omron HEM-705CP monitor (n = 212 recordings). In the longitudinal cohort, mean +/- 2 SD were calculated for blood pressure levels throughout pregnancy. Individual variation in home Omron minus office mercury throughout pregnancy was determined. In preeclampsia, back-to-back blood pressure measurements by the two methods were correlated and quantified as being within 5, 10, and 15 mm Hg. Bland-Altman plots were calculated, and the sensitivity of the Omron HEM-705CP monitor to detect hypertension that was identified by mercury sphygmomanometry was evaluated. RESULTS: At 10 to 14, 19 to 22, 27 to 30, and 35 to 37 weeks of gestation, the upper limits for normal systolic blood pressure levels with the use of home Omron HEM-705CP monitor measurements were 132, 130, 133, and 138 mm Hg and for diastolic blood pressure levels were 82, 79, 81, and 88 mm Hg, respectively. For women who were normotensive and had preeclampsia (although group mean blood pressure values by mercury sphygmomanometry and Omron HEM-705CP monitor were similar), there were marked individual differences (! 40 mm Hg) between the devices. In preeclampsia, paired Omron monitor and mercury systolic and diastolic blood pressure levels were within 5, 10, and 15 mm Hg in 47%, 73%, and 82%, and 56%, 78%, and 92%, respectively. The Omron monitor identified > 90% of mild hypertension (140/90 mm Hg) but missed one third of hypertension with a blood pressure level of > 160/100 mm Hg by mercury sphygmomanometry. CONCLUSION: Clinicians should be aware of the potential differences between blood pressure measurements with mercury sphygmomanometers and Omron HEM-705CP monitors in pregnancy. The Omron HEM-705CP monitor should not be used to monitor hypertension in preeclampsia.