24-hour mean of ambulatory blood pressure for diagnosing gestational hypertension and preeclampsia

The use of ambulatory blood pressure (BP) monitoring (ABPM) has provided a method of BP assessment that may compensate for some of the limitations of isolated measurements. The authors here aim to examine prospectively the effectiveness of the commonly used 24-hour mean as a potential screening test for the early identification of gestational hypertension and preeclampsia. The authors analyzed 503 BP series from 71 healthy pregnant women and 256 series from 42 women who developed gestational hypertension or preeclampsia. BP was sampled at half-hour intervals during the day and hourly during the night for about 48 hours once every four weeks after the first visit to the hospital. Sensitivity slightly increases from the first to the third trimester of gestation, with values ranging from 31.8% for diastolic BP (DBP) in the second trimester to 84.1% for systolic BP (SBP) in the third trimester. Specificity, however, is as low as 6.9% for DBP in the first trimester. The positive predictive value does not reach 55% for any variable in any trimester, too low for a proper individualized diagnosis of gestational hypertension or preeclampsia. The advantages of ABPM over conventional casual sampling do not provide a proper test when relying for diagnosis in the 24-hour mean.