The measurement of diastolic blood pressure during pregnancy: which Korotkoff phase should be used?

Abstract

The aim of this study was to compare the two Korotkoff phases, to estimate diastolic blood pressure during pregnancy. A cohort of 1194 nulliparous pregnant women were followed up prospectively from the twentieth week of pregnancy until delivery. Blood pressure measurements were obtained with random-zero sphygmomanometers at 20, 23, 25, 27, 31, and 35 weeks and then weekly until delivery. After 10 minutes of rest five blood pressure measurements were obtained in each position: supine, lateral, and seated. Korotkoff phases IV and V were obtained in each measurement. The frequency of 0 values was always < 0.5% (n = 10,501 in each time and position). Mean differences between both phases throughout pregnancy fluctuates around 6 mm Hg. Minor differences (mean 3.7 mm Hg) without outlier values were observed in women with diastolic hypertension. Phase 5 showed a better association with other outcome variables related to hypertension, such as proteinuria, intrauterine growth retardation, and hyperuricemia. Considering that phase 5 is easier to obtain, its use implies very few 0 values, that the difference between the two Korotkoff phases is around 6 mm Hg, and that the association with hypertension-related complications is similar to that of phase 4.