Miniature electronic blood pressure monitor compared with a blind-reading mercury sphygmomanometer in pregnancy.

The use of electronic blood pressure monitors is increasing, but they have received little evaluation in pregnancy. We compared an electronic monitor (Nissei D-175 Digital Monitor) with a London School of Hygiene blind-reading mercury sphygmomanometer in clinical conditions in 41 patients in the third trimester. In 141 comparisons, the electronic monitor read systolic pressures that were 16.53 mmHg higher on average than the mercury sphygmomanometer, the limits of agreement being from -9.13 mmHg to +42.19 mmHg. For diastolic pressures, the electronic monitor read 9.71 mmHg higher on average than the mercury sphygmomanometer, the limits of agreement being from -16.97 mmHg to +36.39 mmHg. The coefficient of repeatability was similar for both instruments with systolic and diastolic readings. As much caution should be exercised with the use of the electronic monitor in late pregnancy as with the mercury sphygmomanometer, and practitioners should be aware of the marked differences that can occur between instruments.