Ambulatory blood pressure monitoring, uterine resistances and cardiovascular tests as predictors of pregnancy-induced hypertension

Abstract

Several blood pressure (BP) and autonomic abnormalities have been associated with pregnancy-induced hypertension (PIH) but no noninvasive method has been identified as able to predict the development of PIH. In the present study we examined prospectively 45 consecutive normotensive pregnant women aged 29.9 + 3.3 years at 27 + 4 gestational week, referred to an institutional tertiary care referral center for known risk factors for developing PIH: pre-eclampsia and/or intrauterine growth retardation in previous pregnancy, or abnormal laboratory tests in present pregnancy (hypocalcemia, hyperuricemia). The following tests were performed: echo-Doppler of uterine arteries to evaluate utero-placental resistance index (URI), ambulatory blood pressure monitoring (ABPM) to measure the systolic and diastolic MESOR (Midline Estimating Statistic of Rhythm) defined as the average value of the rhythmic function fitted to the blood pressure data, cardiovascular tests to evaluate the autonomic nervous function (Valsalva manoeuvre, deep breathing test, lying-to-standing test, cold pressor test, isometric handgrip, and power spectral analysis of heart rate variability). Unpaired t test was used to evaluate differences between normotensive and hypertensive women. The logistic regression model with backward selection was used to estimate the probability of PIH. Eighteen women (40 %) developed gestational hypertension. Compared to normotensives, women who developed PIH showed higher systolic (120 ± 6 vs. 114 ± 8 mm Hg respectively; p<0.05) and diastolic MESOR (75 ± 4 vs. 68 ± 5 mm Hg respectively; p< 0.001). The systolic response to Valsalva manoeuvre was significantly increased in women who developed PIH with respect to normotensives (35 ± 10 vs. 29 ± 9 mm Hg, respectively; p<0.05) indicating a sympathetic activation in women with PIH. Power spectral analysis of heart rate variability did not show any significant difference between normotensive women and women who developed PIH. No difference in URI was found between subjects developing hypertension and normotensive women. Logistic regression analysis showed that all variables correctly predicted 88.9% normotensive women and 83.3% women who developed hypertension. Overall prediction was 86.7%. The most relevant parameter for predicting the development of PIH was diastolic MESOR. Cardiovascular tests improved the prediction of PIH. The study shows that ABPM could have a role in the screening of pregnant women at risk of developing hypertension.