Significance of correIations:*p < 0.001; tp < 0.01; SBP = Maternal systolic blood pressure. DBP = Maternal diastolic blood pressure. PP = Maternal pulse pressure. II = Interval index. DI = Differential index.

stolic blood pressures at this stage behave differently from those in term pregnancy. The systolic and diastolic blood pressures in the present study, curiously enough, had no correlation with each other (r = 0.17). They seem to be independent variables, which is not the case in term and midtrimester pregnancies.’ In our previous report we considered the correlation between systolic and diastolic pressures to be autocorrelations, but the present study suggests that this presumption is not justified. The reason for and the basic mechanism behind this phenomenon remain obscure.