Changes in blood pressure in two types (absolute and relative) of pregnancy induced hypertension (hypertensive type of toxemia)
Tomoda, S.; Hidaka, A.; Kitanaka, T.; Nakamoto, O.; Sugawa, T.
Nihon Sanka Fujinka Gakkai Zasshi 44(3): 289-296
1992
ISSN/ISBN: 0300-9165 PMID: 1607750 Document Number: 391793
The criteria for pregnancy induced hypertension (PIH: hypertensive type of toxemia) have been determined by the Japanese Obstetrics and Gynecology Society. Mild PIH is classified into two types. One is "Absolute PIH (A-PIH)" diagnosed by (1) systolic blood pressure (SBP) > = 140 mmHg and < 160 mmHg or (2) diastolic blood pressure (DBP) > = 90 mm Hg and < 110 mmHg. The other one is "relative-PIH (P-RIH)" diagnosed by (3) an increase in SBP > = 30 mmHg compared to the usual SBP or (4) an increase in DBP > = 15 mm Hg compared to the usual DBP (In this paper, blood pressure prior to the 12th gestational week is considered as "usual" blood pressure). However, there has been no report in which two types of PIH are assessed. Our hypothesis is that the pathophysiology of the two types of PIH is different. We have already reported the clinical background of two types of PIH. The purpose of this study is to clarify the pathophysiological difference by evaluating the blood pressure change during pregnancy. We evaluated 963 nullipara and 747 multipara whose pregnancies were recorded from the 1st trimester (multiple pregnancy and pre-term delivery before the 32nd gestational week were excluded). Among the nullipara, 765 women (79.4%) were diagnosed as having normal blood pressure (N-group), 7.1% as A-PIH, and 13.0% as R-PIH. Among the multipara, the N-group consisted of 632 women (84.6%), the A-PIH: 4.6% and R-PIH: 10.3%. A-PIH cases have higher SBP and DBP than the N-group and R-PIH group both among nullipara and multipara. These results suggests that A-PIH cases have some constitution and/or cocult disease which causes the basal blood pressure to increase. The N-group shows a decrease in DBP: 5.3 .+-. 10.7 mmHg in nullipara and 4.4 .+-. 11.3 mmHg in multipara through the 15th .apprx. 18th gestational week compared to the 9th gestational week. The characteristics of R-PIH are an early drop in blood pressure in the 9th gestational week and a late increase after the 33rd gestational week. When we reevaluated R-PIH, considering the blood pressure at 4 .apprx. 6 weeks puerperium as "usual" blood pressure, 97 of 126 R-PIH (77.0%) in nullipara and 64 of 77 R-PIH (83.1%) in multipara were classified in the N-group. In conclusion, A-PIH is a different entity from R-PIH, and also A-PIH is regarded as a hypertension-prone type and R-PIH is regarded as an unstable regulation of vascular dilation.