Interpretation
We observed that the CDXP measured blood pressure as reliable as the Omron M6 Comfort, which has been validated for the use during pregnancy. We did not find any association between body mass index, gestational age, upper arm or wrist circumference, or height of blood pressure and the difference between the CDXP and gold standard. Literature reports similar ranges of deviation of upper-arm devices22, 24. Although blood pressure measurement using an upper-arm device is thought to be superior, we did not detect clinically relevant differences25. The above implies that the CDXP seems to qualify for the use for home blood pressure monitoring.
Our study showed that OBPM under our regular check-up circumstances (several minutes after entering the consult room with the physician present) is significantly higher than the self-measured blood pressure under more standardized conditions: 5 minutes of rest, sitting in a chair against the backrest, non-crossed legs placed on the ground and no physician present. This is in line with literature on pregnant and non-pregnant individuals 28, 30, 31. ‘White coat hypertension’ may lead to overdiagnosis of hypertension when blood pressure is not measured under ideal circumstances 29. Self-measuring blood pressure with the CDXP helps to meet these criteria.
The blood pressure used for monitoring and early detection of pregnancy-related disorders needs to represent the blood pressure during the day. We observed that HBPM using the CDXP during pregnancy is completely stable during the day. Self-measured home blood pressure at a single time point gives a good reflection of the blood pressure during the day. Several studies show comparable differences between OBPM and HBPM in both pregnant and non-pregnant subjects 26-28, 32. Our data is also in line with Hermida et al., that demonstrated that blood pressure is very stable during daytime and drops during the night 4. This implies that HBPM gives a better reflection of the actual blood pressure during pregnancy than OBPM.
The success of changing OBPM to self-measured HBPM also depends on user experience and satisfaction. Our study is in line with previous literature, where 98% of women with gestational hypertensive disease liked involvement in their blood pressure management and declared to have more confidence in HBPM to represent their usual blood pressure16, 33, 34. Our study showed that pregnant women liked the idea of self-measuring their blood pressure, they found the CDXP easy to use and they felt confident about the reliability of their self-measured blood pressure.