DETERMINING BLOOD-PRESSURE IN PREGNANCY - POSITIONAL HYDROSTATIC EFFECTS

OBJECTIVE: To evaluate positional hydrostatic effects on blood pressur e determination during pregnancy. STUDY DESIGN: We studied 30 normoten sive, pregnant women at 34-41 weeks of gestation. Blood pressures were taken in the sitting, left lateral, right lateral and supine position s with a two-minute stabilization period between positions. The bisacr omial diameter suns measured. Multivariate analysis of variance for re peated measures was used to evaluate the affect of position on blood p ressure. RESULTS: Mean systolic pressure in the right arm was 2.6 mm H g greater than that in the left arm (P<.05). There was no difference b etween the arms in diastolic blood pressure. Immediate blood pressure in the lower arm was MO greater than in the higher arm in lateral posi tions, and there were MO other significant positional effects. Observe d blood pressures were significantly different than those theoreticall y expected on the basis of hydrostatic effects (P<.0001).CONCLUSION: P ositional effects on blood pressure in the lateral positions do not ap pear immediately (within two minutes), indicating that hydrostatic pre ssure does not account for these changes. The well-documented blood pr essure reduction from longer duration in the lateral position does not appear to be an artifact of hydrostatic effect. Repositioning pregnan t women in the supine position to have the cuff at the level of the he art is unnecessary and often undesirable when fetal perfusion is an im portant consideration. We suggest that American Heart Association bloo d pressure guidelines stating that all measurements be taken with the cuff at the level of the heart to avoid hydrostatic pressure change be revised for pregnancy.