Measuring blood pressure in pregnant women: a comparison of direct and indirect methods

Am J Obstet Gynecol. 1994 Sep;171(3):661-7. doi: 10.1016/0002-9378(94)90079-5.


Objectives: Our goals were to determine (1) whether Korotkoff phase IV or V sound was a more accurate measure of diastolic blood pressure in pregnancy and (2) interobserver variability of mercury sphygmomanometry of pregnant women.

Study design: Direct (intraarterial) and indirect (mercury sphygmomanometry) blood pressures were compared in 28 pregnant women. Interobserver variability was assessed in a separate study of 86 pregnant women using four highly trained observers.

Results: (1) Routine sphygmomanometry underestimated direct systolic pressure by 11 (3, 18) mm Hg, p < 0.001 (median, interquartile range of differences). Phase IV Korotkoff sound overestimated direct diastolic pressure by 9 (2, 12) mm Hg (p < 0.001) and phase V by 4 (2, 7) mm Hg (p = 0.04). Phase V-recorded diastolic pressure was closer to direct diastolic pressure significantly more often (75%) than was phase IV-recorded diastolic pressure (21%) (p = 0.003). Mean arterial pressures did not differ significantly according to the method used. (2) Median blood pressures did not differ among the four observers for systolic, diastolic phase IV, or phase V recordings. Maximum difference for blood pressure recording among observers was 4 (2, 6) mm Hg.

Conclusions: Auscultatory sphygmomanometry in pregnant women underestimates systolic and overestimates diastolic blood pressure, but the phase V Korotkoff sound is more likely to represent the true diastolic pressure than is the phase IV sound.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Auscultation
  • Blood Pressure Determination / methods*
  • Blood Pressure*
  • Diastole
  • Female
  • Humans
  • Observer Variation
  • Pregnancy / physiology*
  • Regression Analysis
  • Systole