Blood pressure, edema and proteinuria in pregnancy. 9. Proposal for classification

Abstract

The frequency distributions of blood pressures in large populations fail to show two groups, one normotensive and the other hypertensive. In the spectrum of pressures, some people merely have higher levels than others and division of abnormal from normal is artificial and arbitrary, although it is useful for prognosis. The blood pressure of 140/90 as the conventional dividing line does not seem to be appropriate in pregnant women. From the standpoint of fetal prognosis, a level of 125/75 before the thirty-second week and 125/85 thereafter seems more reasonable. Moreover, those levels are close to the 120/80 that Robinson and Brucer specified as the upper limit of normal for all adults and are close to the 130/70 and 120/80 that the eminent British authority, F.J. Browne, used successively in the diagnosis of hypertensive disorders in pregnancy. If the standard of 125/75 were adopted, however, a quarter of all pregnant women would be hypertensive in the second trimester and half in the last month, which are disturbingly high proportions. For the diagnosis of preeclampsia, a rise in blood pressure probably is more significant than an arbitrary level. The usual blood pressure in midpregnancy merely defines the patient's place in the spectrum. Figure 9-1 indicates that in white nulliparas the diastolic pressure rises an average of 10 mm. Hg in the middle of the third trimester. If the mean and median are close together, greater increases would occur in half of the women. The classification of the American Committee on Maternal Welfare and of the Committee on Terminology of the American College of Obstetricians and Gynecologists specify increases of 30 mm. Hg or more in the systolic or 15 mm. Hg or more in the diastolic pressures as criteria of preeclamptic hypertension. pperhaps the rise in diastolic pressure should be set at some greater value. Our analysis of data made thus far cannot decide that issue. The next phase of the study will include analyses in individual women of the times, magnitudes, persistence or transience, and the like of changes in blood pressure, edema, and proteinuria. Such data will afford much more information than can be derived from the preliminary studies reported here. Although edema of the hands and face may be more common in preeclamptic than in normal women, such edema is so common in normal pregnancy as to suggest that it usually is normal. In our data, edema seems to bear no relation to hypertension or proteinuria. The triad of signs -- hypertension, proteinuria, and edema -- is generally accepted as characteristic, though far from specific for preeclampsia. Our data support Hytten's conclusion that edema should by dropped from the triad. There is some indication, however, that some edema is abnormal and that it is associated with an adverse effect when it coincides with proteinuria late in pregnancy.