Second trimester ambulatory blood pressure in nulliparous pregnancy: a useful screening test for pre-eclampsia?

Blunted Overnight Blood Pressure Dipping in Second Trimester; A Strong Predictor of Gestational Hypertension and Preeclampsia

Background:

Preeclampsia is a global burden with 10 million incidences annually and 210 daily deaths worldwide. Diagnosis is mainly based on the features following full presentation.

Objective:

This study explored whether early pregnancy circadian changes of ambulatory blood pressure monitoring (ABPM) could predict preeclampsia and hypertension.

Methods:

In a prospective study, 294 pregnant women who were referred to Sarem Women’s Hospital, Iran were recruited. Systolic, diastolic and mean arterial pressures (MAP) were recorded (diurnally and nocturnally) in each trimester. Dipping was defined as a minimum 10% decrease in blood pressure.

Results:

Of the 251 women who completed the study, 25 percent (n=63) experienced blunted MAP dipping during sleep phases in the second trimester. Eighty-nine percent (n=56) experienced hypertensive disorder in the third trimester, one-third of which experienced preeclampsia. Of the women with normal MAP dipping (n=188), 5 percent (n=10) had gestational hypertension and 1 percent (n=2) became preeclamptic. (P<0.0001).

Conclusion:

This study clearly demonstrated blunted blood pressure dipping overnight during the second trimester which is a strong predictor of forthcoming pregnancy-induced hypertension and preeclampsia. A scoring system was developed to predict hypertensive disorder and it was significantly correlated with preeclampsia occurrence.

Early prediction of preeclampsia

Effective screening for the development of early onset preeclampsia (PE) can be provided in the first-trimester of pregnancy. Screening by a combination of maternal risk factors, uterine artery Doppler, mean arterial pressure, maternal serum pregnancy-associated plasma protein-A, and placental growth factor can identify about 95% of cases of early onset PE for a false-positive rate of 10%.

Prediction of preeclampsia by mean arterial pressure at 11-13 and 20-24 weeks' gestation

OBJECTIVES

To assess the performance of screening for preeclampsia (PE) by mean arterial pressure (MAP) at 11-13 and at 20-24 weeks' gestation.

METHODS

MAP was measured at 11-13 and 20-24 weeks in 17,383 singleton pregnancies, including 70 with early PE, requiring delivery <34 weeks' gestation, 143 with preterm PE, delivering <37 weeks and 537 with total PE. MAP was expressed as multiple of the median (MoM) after adjustment for maternal characteristics and corrected for adverse pregnancy outcomes. The performance of screening for PE by maternal characteristics and MAP MoM at 11-13 weeks (MAP-1), MAP MoM at 20-24 weeks (MAP-2) and their combination was evaluated.

RESULTS

In screening by maternal characteristics and MAP-1, at a false-positive rate (FPR) of 10%, the detection rates (DR) of early PE, preterm PE and total PE were 74.3, 62.9 and 49.3%, respectively; the DR at FPR of 5% were 52.9, 42.7 and 35.8%. In screening by MAP-1 and MAP-2 the DR at FPR of 10%, were 84.3, 65.7 and 52.5%; the DR at FPR of 5% were 60.0, 49.7 and 37.6%, respectively.

CONCLUSIONS

Performance of screening for PE by MAP is best when measurements are taken at both 11-13 and 20-24 weeks' gestation than at only one of these gestational ranges.

Prognostic value of ambulatory blood pressure measurements for the diagnosis of hypertension in pregnancy

Several studies have indicated that the use of the 24 h mean blood pressure, mainly using reference thresholds derived from general nonpregnancy practice, does not provide an effective test for an individualized early diagnosis of hypertension in pregnancy, thus concluding that ambulatory blood pressure monitoring is not a valid approach in pregnancy. With the use of ambulatory blood pressure monitoring, epidemiologic studies have reported gender differences in the circadian variability of blood pressure and heart rate. Typically, men exhibit a lower heart rate and higher blood pressure than women, the differences being larger for systolic than for diastolic blood pressure. Moreover, normotensive and hypertensive pregnant women are characterized by differing but predictable patterns of blood pressure variability throughout gestation. However, the diminished blood pressure in nongravid women as compared with men, the added decrease in blood pressure during the second trimester of gestation in normotensive but not in hypertensive pregnant women and the large amplitude of the circadian pattern that characterizes the blood pressure of healthy pregnant women at all gestational ages, have not been taken into account when establishing reference thresholds for the diagnosis of hypertension in pregnancy. This review will describe these issues, summarize previous results from independent groups on the prognostic value of ambulatory blood pressure monitoring in pregnancy, propose answers as to an accurate reference threshold for blood pressure at different stages of gestation and suggest how this information should be used in order to identify those women at a higher risk of hypertension, who will also be more suitable for prophylactic and/or therapeutic intervention in the early stages of pregnancy.

Twenty-four-hour ambulatory blood pressure monitor heart rate: a potential marker for gestational hypertension in at-risk women

We prospectively correlated the 24-hour ambulatory blood pressure measurements (ABPM) to conventional sphygmomanometer blood pressure measurements (CSM) in women at risk for gestational hypertensive disorders (GHTNDs) and identified predictive factors from ABPM for GHTND. We analyzed 73 women with ≥ 1 risk factor for developing a GHTND. Using both the CSM and ABPM, the systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), and heart rate (HR) were measured for 24 hours during three periods (14 to 24 weeks; 24 to 32 weeks; and 33 weeks to delivery). Correlation between the CSM and ABPM lessened as pregnancy progressed. Seventeen (25%) of women developed a GHTND. MAP variability increased in the GHTND group versus those without a GHTND. The odds of developing a GHTND increased 1.5 times for every 1 beat per minute increase in the ABPM 24-hour HR at visit 1 and reversed by visit 3. In women at risk for a GHTND, CSM and ABPM correlate less well as pregnancy advances. HR changes in at-risk women may be a marker for the development of a GHTND and may reflect increased sympathetic activity and/or decreased baroreceptor sensitivity.

Hypertensive disorders in pregnancy: screening by systolic diastolic and mean arterial pressure at 11-13 weeks

OBJECTIVES

To examine the performance of screening for hypertensive disorders in pregnancy and to compare systolic blood pressure (BP), diastolic BP, and mean arterial pressure (MAP) measured by validated automated devices in a large population of pregnant women at 11-13 weeks.

METHODS

We recorded maternal variables and measured BP by automated devices in 9149 women with singleton pregnancies. The performance of screening for preeclampsia (PE) and gestational hypertension (GH) by combinations of disease-specific maternal factor-derived a priori risk with systolic BP, diastolic BP, and MAP was determined.

RESULTS

There were 8061 cases that were unaffected by PE or GH, 37 that developed PE requiring delivery before 34 weeks (early-PE), 128 with late-PE, and 140 with GH. The systolic BP, diastolic BP, and MAP were significantly higher in early-PE, late-PE, and GH than in the controls (p < 0.0001). The systolic BP was significantly higher in early-PE than in late-PE (p = 0.008) and both systolic BP and MAP were significantly higher in early-PE than in GH (p < 0.01). The best performance in screening was provided by MAP. The detection rate of early-PE at a 10% false-positive rate increased from 47% in screening by maternal factor-derived a priori risk alone to 76% in screening by its combination with MAP. The respective detection rates for late-PE increased from 41 to 52% and for GH increased from 31 to 48%.

CONCLUSION

The measurement of BP can be combined with the maternal factor-derived a priori risk to provide effective first-trimester screening for PE and GH.

Circadian Blood Pressure Variability in Normotensive Pregnant Women as a Function of Parity, Maternal Age, and Stage of Gestation

Studies based on conventional office blood pressure (BP) measurements concluded that both maternal age and parity have significant effects on BP during pregnancy. Previous results have also indicated predictable trends of BP variability with gestational age. Accordingly, we have evaluated possible differences in the circadian pattern of ambulatory BP as a function of parity, maternal age, and stage of gestation in normotensive women who were systematically studied by ambulatory BP monitoring during their pregnancies. We analyzed 1408 BP profiles obtained from 126 nulliparous and 109 multiparous pregnant women sampled for 48 consecutive h every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery. Data were divided for comparative analysis according to parity (nulliparous versus multiparous), age (< or = 25, 26-30, 31-35, and > or = 36 yrs), and trimester of gestation. Circadian BP parameters established by population multiple-components analysis were compared between groups using a nonparametric test. A highly statistically significant circadian pattern described by a model that includes components with periods of 24 and 12h is demonstrated for systolic and diastolic BP for all groups of pregnant women in all trimesters (always p < 0.001). There was no significant difference in the 24h mean among groups divided by parity at any age or stage of pregnancy. A trend of increasing BP with age was found for diastolic but not for systolic BP. Although statistically significant, differences in the 24h mean of diastolic BP among groups divided by age were always less than 2 mm Hg. Data obtained from systematic ambulatory monitoring in normotensive pregnant women indicate the lack of differences in BP according to parity. The small, although significant, increase in diastolic BP with age may have scarce influence in the proper identification of women with gestational hypertension. Reference thresholds for BP to be used in the early identification of hypertensive complications in pregnancy could thus be developed as a function of the rest-activity cycle and gestational age only, and independently of parity or maternal age.

Factors predisposing to pre-eclampsia in women with gestational diabetes

BACKGROUND

Lipid abnormalities occur before the onset of pre-eclampsia but their role in its pathogenesis is unclear. We tested the hypothesis that lipid abnormalities precede and contribute to the development of pre-eclampsia using women with gestational diabetes (GDM) as a focus population.

METHODS

One hundred and eighty-four women with a diagnosis of GDM were studied. Anthropometry, blood pressure, fasting lipids, glucose homeostasis, markers of inflammation and endothelial damage were measured and family history of disease was assessed to determine those measures at diagnosis of GDM that best predicted the development of pre-eclampsia.

RESULTS

Twelve percent of women with GDM developed pre-eclampsia. At diagnosis of GDM, total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol and triglycerides were not different in women who subsequently developed pre-eclampsia (GDM-PE). GDM-PE had elevated body mass index, blood pressure, fasting glucose, insulin, uric acid, and C-reactive protein (CRP), which have all been linked with the 'metabolic syndrome'. They had a greater degree of microalbuminuria and more frequently reported a family history of hypertension and maternal gestational diabetes. In logistic regression, the significant independent predictors for developing pre-eclampsia were fasting glucose, CRP, a family history of hypertension and the proband's mother having gestational diabetes.

CONCLUSION

The results suggest that, in GDM, increased severity of insulin resistance and related features of the 'metabolic syndrome', rather than lipid abnormalities, are precursors to the development of pre-eclampsia and hence are likely to be implicated in the pathophysiology of this disorder. Moreover, these women are likely to be at particularly high risk of long-term cardiovascular disease and Type 2 diabetes.

Differences in Circadian Pattern of Ambulatory Pulse Pressure Between Healthy and Complicated Pregnancies

With the use of ambulatory monitoring, a circadian blood pressure pattern has been shown to characterize normotensive as well as hypertensive pregnant women. However, the potential differences between healthy and complicated pregnancies in pulse pressure, an independent marker of cardiovascular risk in the general population, have not yet been investigated. We analyzed 2523 blood pressure series sampled for 48 hours once every 4 weeks from the first obstetric visit until delivery in 245 women with uncomplicated pregnancies, 140 with gestational hypertension, and 49 who developed preeclampsia. Compared with uncomplicated pregnancies, a statistically significant elevation in the 24-hour mean of pulse pressure is found in complicated pregnancies in all trimesters (P<0.001). Results further indicate similar 24-hour mean of pulse pressure between gestational hypertension and preeclampsia in the first trimester of pregnancy (P=0.158). The increase in pulse pressure among women who developed preeclampsia compared with women with gestational hypertension, although small, was statistically significant in the second trimester (1.4 mm Hg; P=0.010) and, to a larger extent, in the third trimester of pregnancy (1.8 mm Hg; P<0.001). The differences in pulse pressure between healthy and complicated pregnancies, observed already in the first trimester of gestation, are found when systolic and diastolic blood pressure for women with a later diagnosis of gestational hypertension or preeclampsia are within the accepted range of normotension. Moreover, ambulatory pulse pressure provides higher sensitivity than clinic measurements for the diagnosis of hypertension in pregnancy.

Valoración prospectiva del test de tolerancia hiperbárica en el diagnóstico de hipertensión gestacional y preeclampsia

BACKGROUND AND OBJECTIVE

Recent studies have tried to overcome poor results from isolated blood pressure values in detecting hypertension in pregnancy by relying on ambulatory monitoring. Low sensitivity of the 24-hour mean has led many authors to conclude that ambulatory monitoring is not a valid approach in pregnancy. Against this background, we have evaluated prospectively the sensitivity and specificity in the diagnosis of gestational hypertension of the tolerance-hyperbaric test. This is a combined approach consisting of establishing tolerance intervals for the circadian variability of blood pressure as a function of gestational age, and then computing the hyperbaric index (area of blood pressure excess above the upper limit of the interval) by comparison of any patient's blood pressure profile with those limits.

PATIENTS AND METHOD

We studied 328 women who provided a 2014 blood pressure series. They were sampled for 48 hours once every 4 weeks from the first obstetric visit (mostly within the first trimester of gestation) until delivery. The hyperbaric index of each blood pressure series was calculated by taking into account the reference circadian tolerance limits established from a 497 series previously sampled from an independent reference group of 189 normotensive pregnant women.

RESULTS

Sensitivity of the tolerance-hyperbaric test was 91% for women sampled during the first trimester of gestation, and increased up to 99% in the third trimester. Specificity was above 99% in all trimesters. Positive and negative predictive values were above 96% in all trimesters. Moreover, the hyperbaric index provided an early identification of subsequent gestational hypertension and preeclampsia, on the average of 23 weeks prior to the clinical confirmation of the disease.

CONCLUSIONS

The tolerance-hyperbaric test represents a reproducible, stable, noninvasive, and high sensitivity test for the very early identification of subsequent gestational hypertension and preeclampsia, which can also be used as a guide for establishing prophylactic or therapeutic interventions.

Reproducibility of the tolerance-hyperbaric test for diagnosing hypertension in pregnancy

BACKGROUND

The tolerance-hyperbaric test has been shown to provide a valuable approach for the prediction of the outcome of pregnancy. In this test, diagnosis of hypertension is based on the hyperbaric index (area of blood pressure excess above the upper limit of a reference threshold) calculated by comparison with a time-specified tolerance interval for the circadian variability of blood pressure.

OBJECTIVE

To evaluate prospectively the stability and reproducibility of the tolerance-hyperbaric test.

METHODS

We studied 403 women who provided 2430 blood pressure series sampled for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly within the first trimester of gestation) until delivery. Circadian 90% tolerance limits for blood pressure were established as a function of trimester of gestation from 497 series previously sampled from an independent reference group of 189 normotensive pregnant women. Diagnosis of hypertension was established in this trial for each woman in the validation sample on the highly restricted basis of presenting at least one blood pressure profile with a hyperbaric index above the threshold for diagnosis after 20 weeks of gestation.

RESULTS

Sensitivity of the tolerance-hyperbaric test was 93% for women sampled during the first trimester of gestation, and increased to 99% by the third trimester. Specificity was more than 99% in all trimesters. The positive and negative predictive values were greater than 96% in all trimesters.

CONCLUSIONS

The tolerance-hyperbaric test represents a reproducible, stable, non-invasive and high-sensitivity test for the very early identification of subsequent hypertension in pregnancy.

Circadian Blood Pressure Variability as a Function of Parity in Normotensive Pregnant Women

Studies based on office blood pressure measurements concluded that parity has significant effects on blood pressure during pregnancy. The authors evaluated possible differences in the circadian pattern of blood pressure as a function of parity in normotensive women systematically studied by ambulatory blood pressure monitoring. They analyzed 1400 blood pressure series sampled for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 234 women. The circadian pattern of blood pressure variation for each group (nulliparous vs. multiparous) and trimester of gestation was established by population multiple-component analysis. A highly statistically significant circadian pattern, described by a model that includes components with periods of 24 and 12 hours, was demonstrated for systolic and diastolic blood pressure for both groups of pregnant women in all trimesters (p<0.001). There was no significant difference in 24-hour mean among groups divided by parity at any stage of pregnancy (p>0.315). Data obtained from systematic ambulatory monitoring in normotensive pregnant women indicate the lack of differences in blood pressure according to parity. Reference thresholds for blood pressure in pregnancy could thus be developed as a function of rest-activity cycle and gestational age only, independent of parity.

Sampling requirements for ambulatory blood pressure monitoring in the diagnosis of hypertension in pregnancy

Previous studies on ambulatory blood pressure monitoring as a potential screening test for hypertension in pregnancy have not carefully considered sampling requirements. We have examined the impact of duration and frequency of blood pressure sampling in the reproducibility of mean values in pregnancy. We analyzed 2430 blood pressure series sampled every 20 minutes during the day and every 30 minutes at night for 48 hours every 4 weeks from the first obstetric visit until delivery in 235 normotensive and 168 hypertensive pregnant women. Blood pressure series were decimated to generate shorter series with data sampled every 1, 2, 3, or 4 hours for 48 hours, as well as at the original rate for the first day. Reproducibility of mean blood pressure as well as sensitivity and specificity in the diagnosis of hypertension were compared between the original and the decimated series. Sensitivity and specificity of the 24-hour blood pressure mean are similar for the values calculated from the original series and for those obtained from shorter profiles up to data sampled every 3 hours but reduced by 5% to 12% when diagnosis is based on data sampled at 20- to 30-minute intervals for the first 24 hours. Results also indicate that the 24-hour blood pressure mean is better reproduced with data sampled at 3-hour intervals for 48 hours than by data sampled at 20- to 30-minute intervals for 1 day only. This study demonstrates that reproducibility of mean blood pressure values is more dependent on duration of sampling than on sampling rate.

[Circadian blood pressure variation in normal pregnancy, gestational hypertension, and preeclampsia]

BACKGROUND AND OBJECTIVE

Changes in circadian variation of blood pressure could be used either to predict preeclampsia or to assess its severity. With the objective of identifying potential differences in blood pressure at the early stages of pregnancy, we examined and compared the characteristics of circadian variability in blood pressure in healthy and complicated pregnant women who were systematically monitored throughout gestation.

SUBJECTS AND METHOD

We analyzed 2,014 blood pressure series sampled through ambulatory monitoring for 48 hours once every 4 weeks from the first obstetric visit until delivery. The study included 205 women with uncomplicated pregnancy, 92 with gestational hypertension and 31 with preeclampsia. The circadian pattern of blood pressure variation for each group and trimester of gestation was established by means of a population multiple-components analysis.

RESULTS

Differences in the 24-hour mean between healthy and complicated pregnancies were highly significant in all trimesters (p < 0.001), with values of 15.1 and 9.1 mmHg for systolic and diastolic blood presure, respectively, in the third trimester of pregnancy. The 24-hour mean of systolic/diastolic blood pressure for complicated pregnancies was always below 120/72 mmHg. Results further indicated similar circadian characteristics between gestational hypertension and preeclampsia in the first trimester of pregnancy. The difference between these two groups in the 24-hour mean was significant in the second trimester for systolic (3 mmHg; p = 0.002) but not diastolic blood pressure (0.9 mmHg; p = 0.230). In the third trimester, the difference between gestational hypertension and preeclampsia was significant for both variables (5.4 and 3.7 mmHg for systolic and diastolic blood pressure, respectively; p < 0.001).

CONCLUSIONS

The differences in blood pressure between healthy and complicated pregnancies, which are observed as early as the first trimester of pregnancy, are detected when both systolic and diastolic blood pressure measurements in women with a late diagnosis of gestational hypertension or preeclampsia fall within accepted ranges of normotension. These differences offer new end points that may lead to an early identification of hypertensive complications in pregnancy as well as to the establishment of prophylactic interventions.

Circadian rhythm of blood pressure challenges office values as the "gold standard" in the diagnosis of gestational hypertension

Despite poor sensitivity and specificity, office blood pressure (BP) determinations are still the "gold standard" for diagnosing gestational hypertension. This prospective blind study evaluates the prognostic value of office values as compared with ambulatory monitoring in pregnancy. We analyzed 2175 BP series systematically sampled from 355 non-preeclamptic pregnant women for 48 h every 4 wks from the first hospital visit until delivery. Women were divided for comparative purposes into three groups: "detected" gestational hypertension, defined on the basis of casual clinical BP> 140/90 mmHg after 20 wks of gestation and hyperbaric index (area of BP excess above the upper limit of a time-specified tolerance interval adjusted for the circadian pattern of the reference population) consistently above the threshold for diagnosing hypertension in pregnancy; "undetected" gestational hypertension, women with office BP < 140/90 mmHg but hyperbaric index consistently above the threshold for diagnosis; and normotension, women with both office values and hyperbaric index below the respective thresholds for diagnosis. Small and insignificant differences in the 24h mean BP between "detected" and "undetected" gestational hypertension is observed in all trimesters, in contrast with highly significant differences between these two groups and normotensive pregnancies. Normotensive women are characterized by highly significant lesser incidence by 60% in preterm delivery, 70% in intrauterine growth retardation, and 50% in delivery by cesarean section (p < 0.001) compared with women with "detected" and "undetected" gestational hypertension (p > 0.715). In pregnancy, the hyperbaric index is markedly superior to office BP measurements for diagnosis of what should be truly considered gestational hypertension, and for prediction of the outcome of pregnancy.

Prognostic value of office and ambulatory blood pressure measurements in pregnancy

With the objective to assess the prognostic value of office values as compared with ambulatory monitoring in pregnancy, we analyzed 2430 blood pressure series systematically sampled from 403 untreated pregnant women for 48 consecutive hours every 4 weeks from the first visit to the hospital until delivery. Women were divided into 5 groups: "detected" gestational hypertension, women with office blood pressures >140/90 mm Hg after 20 weeks of gestation and hyperbaric index (area of blood pressure excess above the upper limit of a time-specified tolerance interval) consistently above the threshold for diagnosing hypertension in pregnancy; "undetected" gestational hypertension, office values <140/90 mm Hg but hyperbaric index above the threshold for diagnosis; normotension, both office values and hyperbaric index below the thresholds for diagnosis; white coat hypertension, women with recorded diagnosis of gestational hypertension but hyperbaric index consistently below the threshold for diagnosis; and preeclampsia, defined as gestational hypertension and proteinuria. Results indicate small and nonsignificant differences in 24-hour mean of ambulatory pressures between "detected" and "undetected" gestational hypertension at all stages of pregnancy, in contrast with highly significant differences between these two groups and normotensive pregnancies. Average office blood pressure values were similar for preeclampsia, "detected," and "undetected" gestational hypertension. The hyperbaric index was, however, significantly higher for women with preeclampsia after 20 weeks of gestation as compared with all other groups and higher for women with either "detected" or "undetected" gestational hypertension as compared with normotensive pregnant women. The incidence of preterm delivery and intrauterine growth retardation were similar for "detected" and "undetected" gestational hypertension but significantly lower for normotensive women. In pregnancy, the hyperbaric index derived from ambulatory monitoring is markedly superior to office measurements for diagnosis of what should be truly considered gestational hypertension, as well as for prediction of the outcome of pregnancy.

Ambulatory blood pressure as predictor of preeclampsia in diabetic pregnancies with respect to urinary albumin excretion rate and glycemic regulation

BACKGROUND

Twenty-four-hour ambulatory blood pressure was evaluated as a predictor of preeclampsia in women with insulin-dependent diabetes mellitus with respect to urinary albumin excretion rate and glycemic regulation.

METHODS

One hundred and fifty-one women with insulin-dependent diabetes mellitus were consecutively recruited from the outpatient maternity ward for 24 hour ambulatory blood pressure measurement with a portable monitor (SpaceLab 90207). Blood pressure was measured three times during pregnancy and once after delivery. Evaluation was performed with receiver-operator-characteristics curves in primiparous women. Stratified analysis and multiple regression was applied with respect to urinary albumin excretion rate, HbA1c, age, duration of diabetes mellitus, uric acid, and BMI.

RESULTS

The incidence of preeclampsia was significantly associated with increasing urinary albumin excretion rate, primiparity, and ambulatory blood pressure. Ambulatory blood pressure was associated with HbA1c throughout pregnancy adjusted for urinary albumin excretion rate. The ambulatory blood pressure was higher from first trimester throughout pregnancy in women developing preeclampsia compared to women who did not have preeclampsia. The best sensitivity and specificity for predicting preeclampsia in primiparous women were at cut-off values of systolic and diastolic day ambulatory blood pressure above 122 and 74 mmHg, respectively. The relative risk of preeclampsia was significantly higher when ambulatory blood pressure was above the cut-off values and increased further with higher urinary albumin excretion rate.

CONCLUSIONS

The relationship between ambulatory blood pressure and preeclampsia is not confined to women with macroalbuminuria but is also present in women with normo- and microalbuminuria. Poor glycemic control and increased urinary albumin excretion rate is associated with preeclampsia when ambulatory blood pressure is above cut-off values of 122/74 mmHg (systole/diastole). Ambulatory blood pressure is a reliable measurement for prediction of preeclampsia in primiparous women with insulin-dependent diabetes mellitus.

Evaluation of the blood pressure load in the diagnosis of hypertension in pregnancy

The use of a set of new end points obtained from ambulatory blood pressure monitoring, in addition to the blood pressure values themselves, has been advocated to improve sensitivity and specificity in the diagnosis of hypertension and the evaluation of a patient's response to treatment. Among these parameters is the use of blood pressure load, the percentage of values above a given constant reference limit or computed by reference to daytime and nighttime limits. We examined the effectiveness of this parameter as a potential screening test for the detection of hypertension in pregnancy. We analyzed 2014 blood pressure series systematically sampled by ambulatory monitoring for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery of 205 normotensive pregnant women and 123 women who developed gestational hypertension or preeclampsia. The blood pressure load was obtained as the percentage of values >140/110/90 mm Hg (systolic/mean arterial/diastolic blood pressure) during active hours or 120/95/80 mm Hg during resting hours, as well as by comparison with limits obtained by progressively reducing the previous limits by 5 mm Hg, up to a final threshold of 125/95/75 mm Hg (day) and 105/80/65 mm Hg (night). Sensitivity for the blood pressure load computed by reference to the highest limits used here is <55% in all trimesters of pregnancy. The best results were obtained when 130/100/80 mm Hg (day) and 110/85/70 mm Hg (night) were used as references in the third trimester, and when the lowest tested limits of 125/95/75 and 105/80/65 mm Hg were used as references in the first and second trimesters (sensitivity always >73%). The optimum reference limits for calculating the blood pressure load, markedly < mm Hg, must be defined as a function of gestational age, in keeping with the predictable trends in blood pressure along pregnancy previously documented.

Twenty-four-hour automated blood pressure monitoring as a predictor of preeclampsia

OBJECTIVE

The purpose of this study was to determine the predictive ability of parameters of 24-hour ambulatory blood pressure monitoring for the development of preeclampsia or gestational hypertension in women who are already considered at risk for these disorders.

STUDY DESIGN

One hundred twenty-two pregnant women who were considered high risk for the development of preeclampsia underwent 24-hour ambulatory blood pressure monitoring between 18 and 30 weeks gestation, while their condition was normotensive according to routine mercury sphygmomanometry. One hundred sixty-four healthy primigravid women who were considered at usual risk for preeclampsia underwent the same tests as a parallel study. Routine blood pressure, awake and sleep average blood pressure, and 24-hour mean average blood pressure were entered into multiple logistic regression as predictors of either preeclampsia or gestational hypertension; significant variables were then tested by a series of receiver operator curves.

RESULTS

Eight percent of usual risk and 45% of high risk women experienced the development of preeclampsia or gestational hypertension. In both groups, the average routine mercury blood pressure and awake, sleeping, and 24-hour ambulatory blood pressure monitoring-derived blood pressure were significantly higher in women who later experienced the development of preeclampsia or gestational hypertension. In usual risk women, 24-hour systolic blood pressure of >or=115 mm Hg and sleeping systolic blood pressure of >or=106 mm Hg were predictive of later preeclampsia or gestational hypertension, but sensitivities were low (77% and 54%, respectively). In high risk women, sleeping diastolic blood pressure of >or=62 mm Hg and sleeping mean arterial pressure of >or=79 mm Hg were predictive of preeclampsia or gestational hypertension, but again sensitivities were low (70% and 65%, respectively).

CONCLUSION

Awake and sleeping blood pressure are higher in midpregnancy in women who later experience the development of preeclampsia or gestational hypertension. Twenty-four-hour ambulatory blood pressure monitoring provides a noninvasive method of selecting some of these women, but this test has a sensitivity no better than that of other predictive tests, even in women at high risk for preeclampsia.

Predictable blood pressure variability in healthy and complicated pregnancies

With the aim of describing the predictable pattern of blood pressure (BP) variability during gestation, we analyzed 2430 BP series systematically sampled by ambulatory monitoring for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 235 normotensive women, 128 women who developed gestational hypertension, and 40 women who had a final diagnosis of preeclampsia. The pattern of variation along gestation of the 24-hour means of BP and heart rate was established for each group of women by polynomial regression analysis. For normotensive women, results indicate a steady decrease in BP up to 20 weeks of pregnancy, followed by an increase in BP up to the day of delivery, with an average 8% BP increase between the middle of gestation and delivery. In complicated pregnancies, BP is stable until the 22nd week of gestation and then increases linearly for the remainder of the pregnancy. Complicated pregnancies are characterized by a 9% and 13% increase in systolic and diastolic BPs, respectively, during the second half of gestation. Results also indicate that during the first half of pregnancy, systolic but not diastolic BP is slightly elevated in women who developed preeclampsia compared with those who developed gestational hypertension. During the second half of gestation, the linear trend of increasing BP for women who developed preeclampsia has a significantly higher slope than the trend for women with gestational hypertension. For both healthy and complicated pregnancies, heart rate increases until the end of the second trimester and slightly decreases thereafter. This study of women systematically sampled by 48-hour ambulatory BP monitoring throughout gestation confirms the predictable pregnancy-associated variability in BP and provides proper information for the establishment of reference limits for BP to be used in the early diagnosis of hypertensive complications in pregnancy. Those limits should be developed as a function of gestational age, taking into account the trends in BP throughout pregnancy demonstrated here.

Influence of parity and age on ambulatory monitored blood pressure during pregnancy

Studies based on casual blood pressure measurements concluded that both age and parity have significant effects on blood pressure during pregnancy. We have tested these results on clinically healthy normotensive women who were systematically studied by ambulatory blood pressure monitoring during their pregnancies. We analyzed 1254 blood pressure series sampled for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 205 normotensive pregnant women. Data were divided for comparative analysis by parity (nulliparous versus multiparous), age (</=25, 26 to 30, 31 to 35, and >/=36 years), and trimester of gestation. Circadian parameters established by population multiple-component analysis were compared between groups with a nonparametric test. Effects of age and parity on blood pressure were also tested by ANOVA. A highly statistically significant circadian pattern described by a model that includes components with periods of 24 and 12 hours is demonstrated for systolic and diastolic blood pressure for all groups of pregnant women in all trimesters (always P<0.001). There was no significant difference in 24-hour mean among groups divided by parity at any age or stage of pregnancy (always P>0.160). A trend of increasing blood pressure with age was found for diastolic but not systolic blood pressure. Although statistically significant, differences in the 24-hour mean of diastolic blood pressure among groups divided by age were always <1.5 mm Hg. Data obtained from systematic ambulatory monitoring in normotensive pregnant women indicate the lack of differences in blood pressure according to parity. The small, although significant, increase in diastolic blood pressure with age may have little influence in the proper identification of women with gestational hypertension. Reference thresholds for blood pressure to be used in the early identification of hypertensive complications in pregnancy could thus be developed as a function of rest-activity cycle and gestational age, independent of parity or maternal age.

Blood pressure monitoring during pregnancy

Hypertensive disease in pregnancy represents a significant health problem in the world, and ranks second only to thromboembolism as a cause of maternal mortality in the USA. In addition, hypertension is associated with both perinatal morbidity and mortality secondary to direct effects on the fetus as well as the iatrogenic preterm deliveries performed for maternal indications. Conventional (office, mercury column or aneroid manometry) blood pressure measurement is the most common screening test performed during prenatal visits. During the past several years, investigators have focused on the use of 24-h ambulatory and automated self (or home) blood pressure monitoring during pregnancy. This review article summarizes the current literature on both ambulatory and home blood pressure monitoring in pregnancy and how they relate to various clinical aspects of hypertension in pregnancy.

Blood pressure patterns in normal pregnancy, gestational hypertension, and preeclampsia

With the aim to describe the daily pattern of blood pressure during the trimesters of pregnancy in clinically healthy women as well as in pregnant women who developed gestational hypertension or preeclampsia, we analyzed 1494 blood pressure series systematically sampled by ambulatory monitoring for 48 hours every 4 weeks after the first obstetric visit in 124 women with uncomplicated pregnancies, 55 with gestational hypertension, and 23 with a final diagnosis of preeclampsia. The circadian pattern of blood pressure variation for each group and trimester of gestation was established by population multiple-component analysis. A highly statistically significant circadian pattern represented by a linear model that includes components with periods of 24 and 12 hours is demonstrated for systolic and diastolic blood pressure for all groups of pregnant women in all trimesters (P:<0.001 in all cases). The differences in circadian rhythm-adjusted mean between complicated and uncomplicated pregnancies are highly statistically significant in all trimesters (always P:<0.001). There is also a statistically significant difference in circadian amplitude (extent of daily change) of blood pressure between healthy and complicated pregnancies in all trimesters (always P:<0.004). Results further indicate similar circadian characteristics between women who later developed gestational hypertension or preeclampsia in the first trimester of pregnancy. The difference between these 2 groups in circadian mean is statistically significant in the second trimester for systolic (P:=0.022) but not for diastolic blood pressure (P:=0.986). In the third trimester, the difference in circadian mean is highly statistically significant for both variables (P:<0.001). The differences in blood pressure between healthy and complicated pregnancies can be observed as early as in the first trimester of pregnancy. Those highly significant differences are found when both systolic and diastolic blood pressure for women with a later diagnosis of gestational hypertension or preeclampsia are well within the accepted normal physiological range of blood pressure variability. These differing changes in the circadian pattern of blood pressure with advancing gestational age between healthy and complicated pregnancies offer new end points that may lead to an early identification of hypertensive complications in pregnancy as well as to the establishment of prophylactic intervention.

Preeclamptic pregnancy is associated with increased sympathetic and decreased parasympathetic control of HR

Previous work from our laboratory using heart rate variability (HRV) has demonstrated that women before menopause have a more dominant parasympathetic and less effective sympathetic regulations of heart rate compared with men. Because it is still not clear whether normal or preeclamptic pregnancy coincides with alternations in the autonomic functions, we evaluated the changes of HRV in 17 nonpregnant, 17 normotensive pregnant, and 11 preeclamptic women who were clinically diagnosed without history of diabetic neuropathy, cardiac arrhythmia, and other cardiovascular diseases. Frequency-domain analysis of short-term, stationary R-R intervals was performed to evaluate the total variance, low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF; 0.15-0.40 Hz), ratio of LF to HF (LF/HF), and LF in normalized units (LF%). Natural logarithm transformation was applied to variance, LF, HF, and LF/HF for the adjustment of the skewness of distribution. We found that the normal pregnant group had a lower R-R value and HF but had a higher LF/HF and LF% compared with the nonpregnant group. The preeclamptic group had lower HF but higher LF/HF compared with either the normal pregnant or nonpregnant group. Our results suggest that normal pregnancy is associated with a facilitation of sympathetic regulation and an attenuation of parasympathetic influence of heart rate, and such alterations are enhanced in preeclamptic pregnancy.

Ambulatory blood pressure monitoring in pregnancy

Hypertensive disorders of pregnancy remain a major cause of maternal and perinatal morbidity and mortality. Diagnosis and management of these disorders has relied on conventional blood pressure measurement, a technique fraught with error and uncertainty. Ambulatory blood pressure measurement is a promising new technique that has the potential to overcome the inaccuracies of conventional blood pressure measurement. Several ambulatory blood pressure monitors have been validated in pregnant populations, and normal reference ranges have been established. More recent research has focused on the potential clinical roles of ambulatory blood pressure measurement in pregnancy. This review addresses the limitations of conventional blood pressure measurement and reviews the current literature on the application of ambulatory blood pressure measurement in pregnancy.

Blood pressure excess for the early identification of gestational hypertension and preeclampsia

We have examined prospectively whether the combined approach of establishing tolerance intervals for the circadian variability of blood pressure (BP) as a function of gestational age, and then determining the so-called hyperbaric index (area of BP excess above the upper limit of the tolerance interval) by comparison of any patient's BP profile (obtained by ambulatory monitoring) with those intervals provides a high sensitivity test for the early detection of pregnant women who subsequently will develop gestational hypertension or preeclampsia. We analyzed 657 BP series from 92 women with uncomplicated pregnancies and 378 series from 60 women who developed gestational hypertension or preeclampsia. BP was sampled for about 48 hours once every 4 weeks after the first obstetric consultation. Circadian 90% tolerance limits were determined as a function of trimester of gestation from 497 series previously sampled from a reference group of 189 normotensive pregnant women. The hyperbaric index was then determined for each individual BP series in the validation sample. Sensitivity of this test for diagnosing gestational hypertension was 93% for women sampled during the first trimester of gestation and increased up to 99% in the third trimester. The positive and negative predictive values were above 96% in all trimesters. Despite the limitations of ambulatory monitoring, the approach presented here, now validated prospectively, represents a reproducible, noninvasive, and high sensitivity test for the very early identification of subsequent gestational hypertension and preeclampsia, on the average, 23 weeks before the clinical confirmation of the disease.

Reversed circadian blood pressure rhythm preserves fetal growth in preeclamptic pregnancy

OBJECTIVE

To determine the clinical trait of hypertension in pregnant women with a reversed circadian blood pressure (BP) rhythm.

STUDY DESIGN

24-h BP monitoring was performed in 56 hypertensive pregnant women, of whom 12 had a reversed systolic BP (SBP) rhythm (day/night mean BP ratio < 1.0). Clinical data, ultrasound fetometry and umbilical artery velocimetry were compared to that in women with a normal rhythm. Statistical analyses were performed with simple linear regression, Mann-Whitney U test, analysis of variance, contingency table analysis and Fisher's test. A two-tailed P value of < 0.05 was considered significant.

RESULTS

In the reversed SBP group, the nighttime BP, fetal weight, albuminuria and S-urate were higher, and the BP variations smaller. The birthweight correlated negatively to the SBP day/night ratio. Higher SBP day/night ratios and larger BP variations were associated with an increased vascular resistance in the umbilical artery and an impaired growth.

CONCLUSION

A reversed SBP rhythm was associated with a more severe degree of preeclampsia, but also with a smaller BP variation, maintenance of fetal growth, and higher birthweight. A sustained high nighttime BP preserved fetal growth. These novel observations challenge the opinion that a reversed circadian BP rhythm is merely an ominous sign.

Diagnosing gestational hypertension and preeclampsia with the 24-hour mean of blood pressure

The use of ambulatory blood pressure monitoring has provided a method of blood pressure assessment that may compensate for some of the limitations of isolated measurements. Here we aim to examine prospectively the effectiveness of the commonly used 24-hour mean as a potential screening test for the identification of gestational hypertension and preeclampsia. We analyzed 503 blood pressure series from 71 healthy pregnant women and 256 series from 42 women who developed gestational hypertension or preeclampsia. Forty-eight-hour blood pressure monitoring was done once every 4 weeks after the first obstetric consultation. Sensitivity and specificity of the 24-hour mean of blood pressure were computed for each trimester of pregnancy by comparing distributions of values obtained for healthy and complicated pregnancies, without assuming an a priori threshold for diagnosing gestational hypertension on the basis of mean blood pressure. Sensitivity ranges from 31.8% for diastolic blood pressure in the second trimester to 84.1% for systolic blood pressure in the third trimester. However, specificity is as low as 6.9% for diastolic blood pressure in the first trimester. The positive predictive value does not reach 55% for any variable in any trimester. The higher relative risk was consistently obtained for systolic blood pressure (4.9 in the third trimester). Despite the highly statistically significant differences in blood pressure found between healthy and complicated pregnancies in all trimesters, the daily mean of blood pressure does not provide a proper and stable individualized test for diagnosing hypertensive complications in pregnancy. Other indexes obtained from the blood pressure series have been shown, however, to identify early in pregnancy those women who subsequently will develop gestational hypertension or preeclampsia, rendering ambulatory blood pressure monitoring a useful, but still costly, technique in pregnancy.

Circadian blood pressure variability in healthy and complicated pregnancies

With the aim to describe the circadian pattern of noninvasive ambulatorily monitored blood pressure during the trimesters of pregnancy in clinically healthy women as well as in pregnant women who developed gestational hypertension or preeclampsia, we analyzed 759 blood pressure series sampled by ambulatory monitoring for about 48 hours every 4 weeks after the first obstetric visit in 71 women with uncomplicated pregnancies, 28 with gestational hypertension, and 14 with preeclampsia. The circadian pattern of blood pressure variation for each group (complicated versus uncomplicated pregnancies) and trimester of gestation was established by linear least-squares methods. A highly statistically circadian pattern is demonstrated for systolic and diastolic blood pressure for both groups of pregnant women in all trimesters (P<.001 in all cases). Blood pressure decreases from the first trimester to the second and rises again in the third for healthy pregnant women. For women who developed gestational hypertension or preeclampsia, blood pressure is stable during the first half of pregnancy and then continuously increases until delivery. The differences in circadian rhythm-adjusted mean between complicated and uncomplicated pregnancies are highly statistically significant in all trimesters (always P<.001). This study confirms and extends to ambulatory everyday life conditions the predictable circadian variability in blood pressure during gestation. The differences in blood pressure between healthy and complicated pregnancies can be observed as early as the first trimester of pregnancy. Those differences are found when both systolic and diastolic blood pressures for women with a later diagnosis of gestational hypertension or preeclampsia are well within the accepted normal physiological range of blood pressure variability.

Can 24-hour ambulatory blood pressure measurement predict the development of hypertension in primigravidae?

OBJECTIVE

To assess the role of 24-hour ambulatory blood pressure measurement in the mid-second trimester as a predictive test for the development of hypertension in pregnancy.

DESIGN

Prospective intervention.

SETTING

The Rotunda Hospital, Dublin.

PARTICIPANTS

One thousand one hundred and two healthy primigravid women.

INTERVENTION

24-hour ambulatory blood pressure measurement at 18 to 24 weeks of gestation.

MAIN OUTCOME MEASURES

The development of pre-eclampsia or gestational hypertension.

RESULTS

A total of 1048 women had sufficient readings to be included in the final analysis. Of these, 23 (2.2%) developed pre-eclampsia, 64 (6.1%) developed gestational hypertension and 961 (91.7%) remained normotensive. Significantly higher ambulatory blood pressures were recorded in both the pre-eclamptic and gestational hypertensive group compared with the normotensive group. In addition, the gestational hypertensive group had significantly higher clinically measured blood pressure compared with the normotensive group. There were no differences between the pre-eclamptic and the gestational hypertensive group for any of the blood pressure parameters analysed. The best overall predictor for pre-eclampsia was 24-hour mean diastolic pressure which using a cutoff level of 71 mmHg gave a test with a sensitivity of only 22% and a positive predictive value of 15%.

CONCLUSION

Because the absolute differences are small and the overlap between the hypertensive and normotensive groups large, ambulatory blood pressure measurement, in a healthy primigravid population, between 18 and 24 weeks of gestation is not a useful predictor of hypertension.

Conflicting data on intervillous circulation in early pregnancy

According to classic embryological textbooks intervillous circulation is established early in the first trimester. This process starts with trophoblastic invasion of the decidua in which proteolytic enzymes facilitate the penetration and erosion of the adjacent maternal capillaries with formation of the lacunae. After the lacunar or previllous stage trophoblast invades deeper portions of endometrium with belonging spiral arteries. This gradual process finishes with direct opening of the spiral arteries in the intervillous space under the fully developed placenta. This classic concept of establishment of the intervillous circulation was challenged in 1987 and 1988 by the experiments of HUSTIN and SHAAPS. The authors believed that blood flow in the intervillous space is absent in incompletely development before 12 weeks of gestation. After the introduction of the new generation of far more sensitive color Doppler devices in the last few years, our group and several others reported a positive finding of intervillous circulation during the first trimester of pregnancy.

High sensitivity test for the early diagnosis of gestational hypertension and preeclampsia. II. Circadian blood pressure variability in health and hypertensive pregnant women

The aim of this study was to describe the circadian pattern of non-invasive ambulatorily monitored blood pressure during the trimesters of pregnancy in clinically healthy women as well as in pregnant women who developed gestational hypertension or preeclampsia, and to compare sensitivity and specificity of diagnosis based on the average of the blood pressure series with the values obtained on the basis of casual measurements. We analyzed a total of 745 blood pressure series sampled by ambulatory monitoring for about 48 hours in each of several occasions in 189 women with uncomplicated pregnancies, 71 with gestational hypertension, and 29 with preeclampsia. The circadian pattern of BP variation for each group (complicated vs. uncomplicated pregnancies) and trimester of gestation was established by linear least-squares methods. Highly statistically different circadian patterns are demonstrated for systolic, mean arterial and diastolic blood pressure for both groups of pregnant women in all trimesters (P < 0.001 in all cases). Blood pressure decreases from the first trimester to the second and raises again in the third for healthy pregnant women, but continuously increases during gestation in women who developed gestational hypertension or preeclampsia. The differences in circadian rhythm-adjusted mean between complicated and uncomplicated pregnancies are highly statistically significant in all trimesters (P < .001). Sensitivity and specificity of diagnosing gestational hypertension based on the circadian mean are 73% and 48%, respectively, too low for a proper individualized diagnosis of gestational hypertension or preeclampsia. This study confirms the predictable circadian variability in blood pressure during gestation. The differences between healthy and complicated pregnancies can be observed as early as in the first trimester of pregnancy, but the use of the 24-hour mean BP does not provide a good approach for early diagnosis of gestational hypertension or preeclampsia.

Ambulatory blood pressure in pregnancy: comparison of the Spacelabs 90207 and Accutracker II monitors with intraarterial recordings

OBJECTIVE

Our purpose was to compare systolic and diastolic blood pressures obtained with the Spacelabs 90207 (Spacelabs Medical Products, Dee Why, Australia) or Accutracker II (Suntech Medical Instruments, Melbourne, Australia) ambulatory blood pressure monitoring devices with intraarterial blood pressures in pregnant women.

STUDY DESIGN

Direct (intraarterial) and resting blood pressures with the ambulatory blood pressure monitoring device were compared in 39 pregnant women (14 Accutracker II and 25 Spacelabs 90207).

RESULTS

The Accutracker II device underestimated direct systolic pressure by -9 (-13, -3) mm Hg (median, interquartile range) (p = 0.028) but gave similar diastolic pressure. The Spacelabs 90207 device gave similar systolic pressures but overestimated direct diastolic pressure by 7 (2, 12) mm Hg (p < 0.001). Variability for systolic and diastolic blood pressures within subjects was similar with the two devices. Both received poor gradings by standards of the British Hypertension Society and did not meet criteria of the Association for the Advancement of Medical Instrumentation, with intraarterial recordings used as the reference.

CONCLUSIONS

The Accutracker II device significantly underestimated resting direct systolic pressure, whereas the Spacelabs 90207 device significantly overestimated resting direct diastolic pressure in pregnant women. Although poor gradings were achieved for both devices when intraarterial pressures were used as the reference, this is similar to comparisons of routine mercury sphygmomanometry with intraarterial recordings and does not mean these devices are unsuitable for use in pregnancy.