Twenty-four-hour ambulatory blood pressure measurement in a primigravid population

Postpartum-Specific Vital Sign Reference Ranges

Postpartum-specific reference ranges for blood pressure, heart rate, respiratory rate, oxygen saturation, and temperature may facilitate early identification of unwell postpartum women.

To estimate normal ranges for postpartum maternal vital signs.

Setting and techniques for monitoring blood pressure during pregnancy

BACKGROUND

Regular blood pressure (BP) measurement is crucial for the diagnosis and management of hypertensive disorders in pregnancy, such as pre-eclampsia. BP can be measured in various settings, such as conventional clinics or self-measurement at home, and with different techniques, such as using auscultatory or automated BP devices. It is important to understand the impact of different settings and techniques of BP measurement on important outcomes for pregnant women.

OBJECTIVES

To assess the effects of setting and technique of BP measurement for diagnosing hypertensive disorders in pregnancy on subsequent maternal and perinatal outcomes, women's quality of life, or use of health service resources.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) on 22 April 2020, and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) involving pregnant women, using validated BP devices in different settings or using different techniques.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed risk of bias, and used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

Of the 21 identified studies, we included three, and excluded 11; seven were ongoing. Of the three included RCTs (536,607 women), one was a cluster-RCT, with a substantially higher number of participants (536,233 deliveries) than the other two trials, but did not provide data for most of our outcomes. We generally judged the included studies at low risk of bias, however, the certainty of the evidence was low, due to indirectness and imprecision. Meta-analysis was not possible because each study investigated a different comparison. None of the included studies reported our primary outcome of systolic BP greater than or equal to 150 mmHg. None of the studies reported any of these important secondary outcomes: antenatal hospital admissions, neonatal unit length of stay, or neonatal endotracheal intubation and use of mechanical ventilation. Setting of BP measurement: self-measurement versus conventional clinic measurement (one study, 154 women) There were no maternal deaths in either the self-monitoring group or the usual care group. The study did not report perinatal mortality. Self-monitoring may lead to slightly more diagnoses of pre-eclampsia compared with usual care (risk ratio (RR) 1.49, 95% confidence interval (CI) 0.87 to 2.54; 154 women; 1 study; low-certainty evidence) but the wide 95% CI is consistent with possible benefit and possible harm. Self-monitoring may have little to no effect on the likelihood of induction of labour compared with usual care (RR 1.09, 95% CI 0.82 to 1.45; 154 women; 1 study; low-certainty evidence). We are uncertain if self-monitoring BP has any effect on maternal admission to intensive care (RR 1.54, 95% CI 0.06 to 37.25; 154 women; 1 study; low-certainty evidence), stillbirth (RR 2.57, 95% CI 0.13 to 52.63; 154 women; 1 study; low-certainty evidence), neonatal death (RR 1.54, 95% CI 0.06 to 37.25; 154 women; 1 study; low-certainty evidence) or preterm birth (RR 1.15, 95% CI 0.37 to 3.55; 154 women; 1 study; low-certainty evidence), compared with usual care because the certainty of evidence is low and the 95% CI is consistent with appreciable harms and appreciable benefits. Self-monitoring may lead to slightly more neonatal unit admissions compared with usual care (RR 1.53, 95% CI 0.65 to 3.62; 154 women; 1 study; low-certainty evidence) but the wide 95% CI includes the possibility of slightly fewer admissions with self-monitoring. Technique of BP measurement: Korotkoff phase IV (K4, muffling sound) versus Korotkoff phase V (K5, disappearance of sound) to represent diastolic BP (one study, 220 women) There were no maternal deaths in either the K4 or K5 group. There may be little to no difference in the diagnosis of pre-eclampsia between using K4 or K5 for diastolic BP (RR 1.16; 95% CI 0.89 to 1.49; 1 study; 220 women; low-certainty evidence), since the wide 95% CI includes the possibility of more diagnoses with K4. We are uncertain if there is a difference in perinatal mortality between the groups because the quality of evidence is low and the 95% CI is consistent with appreciable harm and appreciable benefit (RR 1.14, 95% CI 0.16 to 7.92; 1 study, 220 women; low-certainty evidence). The trial did not report data on maternal admission to intensive care, induction of labour, stillbirth, neonatal death, preterm birth, or neonatal unit admissions. Technique of BP measurement: CRADLE intervention (CRADLE device, a semi-automated BP monitor with additional features, and an education package) versus usual care (one study, 536,233 deliveries) There may be little to no difference between the use of the CRADLE device and usual care in the number of maternal deaths (adjusted RR 0.80, 95% CI 0.30 to 2.11; 536,233 women; 1 study; low-certainty evidence), but the 95% CI is consistent with appreciable harm and appreciable benefit. The trial did not report pre-eclampsia, induction of labour, perinatal mortality, preterm birth, or neonatal unit admissions. Maternal admission to intensive care and perinatal outcomes (stillbirths and neonatal deaths) were only collected for a small proportion of the women, identified by an outcome not by baseline characteristics, thereby breaking the random allocation. Therefore, any differences between the groups could not be attributed to the intervention, and we did not extract data for these outcomes.

AUTHORS' CONCLUSIONS

The benefit, if any, of self-monitoring BP in hypertensive pregnancies remains uncertain, as the evidence is limited to one feasibility study. Current practice of using K5 to measure diastolic BP is supported for women with pregnancy hypertension. The benefit, if any, of using the CRADLE device to measure BP in pregnancy remains uncertain, due to the limitations and instability of the trial study design.

Pre-conception blood pressure and evidence of placental malperfusion

Background

Evidence of placental maternal vascular malperfusion is associated with significant perinatal outcomes such as preeclampsia, intrauterine growth restriction and preterm birth. Elevations in pre-pregnancy blood pressure increase the risk for poor perinatal outcomes; however, the evidence linking pre-pregnancy blood pressure and placental malperfusion is sparse.

Materials and methods

We conducted a retrospective case-control study of women with singleton gestations with placental evaluations who delivered at Magee-Womens Hospital in 2012. Charts from 100 deliveries with placental malperfusion lesions (vasculopathy, advanced villous maturation, infarct, or fibrin deposition) and 102 deliveries without placental malperfusion were randomly selected for screening. Blood pressure, demographic, and clinical data were abstracted from pre-pregnancy electronic medical records and compared between women with and without subsequent placental malperfusion lesions.

Results

Overall, 48% of women had pre-pregnancy records, and these were similarly available for women with and without placental malperfusion. Women with placental malperfusion demonstrated a reduction in their pre- to early pregnancy decrease in diastolic blood pressure (DBP). Adjusted for race, pre-pregnancy BMI, age, pre-conception interval, and gestational age at the first prenatal visit, the difference in pre- to early pregnancy DBP was significantly less in women with placental malperfusion compared to those without this pathologic finding (− 1.35 mmHg drop vs − 5.6mmg, p < 0.05).

Conclusion

A blunted early gestation drop in DBP may be a risk factor for placental malperfusion, perhaps related to early pregnancy vascular maladaptation. The ability of the electronic medical record to provide pre-pregnancy data serves as an underutilized approach to study pre-pregnancy health.

Österreichischer Blutdruckkonsens 2019

Erhöhter Blutdruck bleibt eine Hauptursache von kardiovaskulären Erkrankungen, Behinderung und frühzeitiger Sterblichkeit in Österreich, wobei die Raten an Diagnose, Behandlung und Kontrolle auch in rezenten Studien suboptimal sind. Das Management von Bluthochdruck ist eine häufige Herausforderung für Ärztinnen und Ärzte vieler Fachrichtungen. In einem Versuch, diagnostische und therapeutische Strategien zu standardisieren und letztendlich die Rate an gut kontrollierten Hypertoniker/innen zu erhöhen und dadurch kardiovaskuläre Erkrankungen zu verhindern, haben 13 österreichische medizinische Fachgesellschaften die vorhandene Evidenz zur Prävention, Diagnose, Abklärung, Therapie und Konsequenzen erhöhten Blutdrucks gesichtet. Das hier vorgestellte Ergebnis ist der erste Österreichische Blutdruckkonsens. Die Autoren und die beteiligten Fachgesellschaften sind davon überzeugt, daß es einer gemeinsamen nationalen Anstrengung bedarf, die Blutdruck-assoziierte Morbidität und Mortalität in unserem Land zu verringern.

A randomized-controlled trial to assess the effect of ibuprofen on postpartum blood pressure in women with hypertensive disorders of pregnancy

OBJECTIVES

To test the hypothesis that ibuprofen is equivalent to acetaminophen in its effect on postpartum blood pressure in women with gestational hypertension or preeclampsia without severe features.

STUDY DESIGN

Single-center randomized, crossover, equivalence trial among women with hypertensive disorders of pregnancy without severe features after vaginal delivery. Participants were assigned in a double-blind fashion to ibuprofen 600 mg or acetaminophen 650 mg every 6 h for 24 h followed by crossover to the other drug. We assessed clinical blood pressures and ambulatory blood pressure monitor measurements. Intention-to-treat analyses were performed using a linear mixed model adjusted for time period.

MAIN OUTCOME MEASURES

The mean difference in systolic blood pressure through 24 h of drug exposure with an equivalence margin of 10 mmHg.

RESULTS

Of 185 screened women, 74 enrolled prior to delivery. Forty-three women remained eligible and were randomized to ibuprofen first (n = 20, 46.5%) or acetaminophen first (n = 23, 53.5%). A total of 37 women (86.0%) received study drug (ibuprofen first n = 19, acetaminophen first n = 18). Most participants were white (91.9%) and had gestational hypertension (86.5%); mean (SD) age was 31.0 (6.5) years. The mean adjusted difference in systolic blood pressure was 1.0 mmHg (95% CI, -3.7 to 5.7 mmHg), which was within the equivalence margin. A linear mixed model did not demonstrate a main effect of group assignment, nor did it show an interaction effect with time period.

CONCLUSIONS

Among women with gestational hypertension and preeclampsia without severe features, ibuprofen is an equally safe option as acetaminophen with respect to postpartum blood pressure concerns.

Trends of blood pressure and heart rate in normal pregnancies: a systematic review and meta-analysis

BACKGROUND

Current reference ranges for blood pressure and heart rate throughout pregnancy have a poor evidence base.

METHODS

This is a systematic review and meta-analysis. We included studies measuring blood pressure or heart rate from healthy pregnant women within defined gestational periods of 16 weeks or less. We analysed systolic blood pressure, diastolic blood pressure and heart rate by gestational age. We assessed effects of measurement year and method.

RESULTS

We included 39 studies undertaken in 1967-2017, containing 124,349 systolic measurements from 36,239 women, 124,291 diastolic measurements from 36,181 women and 10,948 heart rate measurements from 8317 women. Mean (95% CI) systolic blood pressure was lowest at 10 weeks gestation, 110.4 (108.5, 112.3) mmHg, rising to 116.0 (113.6, 118.4) mmHg at 40 weeks, mean (95% CI) change 5.6 (4.0, 7.2) mmHg. Mean (95% CI) diastolic blood pressure was lowest at 21 weeks gestation, 65.9 (64.2, 67.7) mmHg; rising to 72.8 (71.0, 74.6) mmHg at 40 weeks, mean (95% CI) change 6.9 (6.2, 7.5) mmHg. Mean (95% CI) heart rate rose from 79.3 (75.5, 83.1) beats/min at 10 weeks to 86.9 (82.2, 91.6) beats/min at 40 weeks gestation, mean (95% CI) change 7.6 (1.8, 13.4) beats/min. Studies using manual measurement reported higher diastolic blood pressures than studies using automated measurement, mean (95 CI) difference 4.9 (0.8, 8.9) mmHg. Diastolic blood pressure increased by 0.26 (95% CI 0.10-0.43) mmHg/year. Including only higher-quality studies had little effect on findings, with heterogeneity remaining high (I2 statistic > 50%).

CONCLUSIONS

Significant gestational blood pressure and heart rate changes occur that should be taken into account when assessing pregnant women. Commonly taught substantial decreases in blood pressure mid-pregnancy were not seen and heart rate increases were lower than previously thought. Manual and automated blood pressure measurement cannot be used interchangeably. Increases in diastolic blood pressure over the last half-century and differences between published studies show contemporary data are required to define current normal ranges.

STUDY REGISTRATION

PROSPERO CRD42014009673.

Thresholds for Ambulatory Blood Pressure Monitoring Based on Maternal and Neonatal Outcomes in Late Pregnancy in a Southern Chinese Population

Background

In contrast to the general population, outcome‐derived thresholds for diagnosing ambulatory hypertension in pregnancy are not yet available. We aimed to identify and compare outcome‐derived ambulatory blood pressure (BP) monitoring thresholds for adverse perinatal outcomes by using approaches related and not related to clinic BP in a southern Chinese population.

Methods and Results

Ambulatory BP monitoring was performed in a cohort of 1768 high‐risk participants in late pregnancy who were not taking antihypertensive medications. Participants were followed for composite maternal (severe complications) and neonatal (pregnancy loss, advanced neonatal care, and small for gestational age) outcomes. Modeling of clinic BP–unrelated approaches revealed a nonlinear threshold effect of ambulatory diastolic BP on the composite outcome, with increased risk for daytime ≥79 mm Hg and 24‐hour measurement ≥76 mm Hg. For other ambulatory BP components showing linear associations with outcome, the following thresholds were identified: 131 mm Hg for daytime systolic, 121 mm Hg for nighttime systolic, 130 mm Hg for 24‐hour systolic, and 73 mm Hg for night‐time diastolic BP. These thresholds unrelated to clinic BP were lower than the equivalents yielding a similar probability of outcome to clinic BP of 140/90 mm Hg and were comparable with equivalents to clinic BP of 130/80 mm Hg.

Conclusions

Using an outcome‐derived approach unrelated to clinic BP, we identified rounded thresholds to define ambulatory hypertension in at‐risk women in late pregnancy in a southern Chinese population as follows: 130/80 mm Hg for daytime, 120/75 mm Hg for nighttime, and 130/75 mm Hg for 24‐hour measurement. For wider clinical applicability and to align both nonpregnancy and pregnancy ambulatory BP monitoring with an outcomes‐based approach, prospective, multiethnic, international studies from early pregnancy onward will be required.

Effects of dietary nitrate supplementation, from beetroot juice, on blood pressure in hypertensive pregnant women: A randomised, double-blind, placebo-controlled feasibility trial

Chronic hypertension in pregnancy is associated with significant adverse pregnancy outcomes, increasing the risk of pre-eclampsia, fetal growth restriction and preterm birth. Dietary nitrate, abundant in green leafy vegetables and beetroot, is reduced in vivo to nitrite and subsequently nitric oxide, and has been demonstrated to lower blood pressure, improve vascular compliance and enhance blood flow in non-pregnant humans and animals. The primary aims of this study were to determine the acceptability and efficacy of dietary nitrate supplementation, in the form of beetroot juice, to lower blood pressure in hypertensive pregnant women. In this double-blind, placebo-controlled feasibility trial, 40 pregnant women received either daily nitrate supplementation (70 mL beetroot juice, n = 20) or placebo (70 mL nitrate-depleted beetroot juice, n = 20) for 8 days. Blood pressure, cardiovascular function and uteroplacental blood flow was assessed at baseline and following acute (3 h) and prolonged (8 days) supplementation. Plasma and salivary samples were collected for analysis of nitrate and nitrite concentrations and acceptability of this dietary intervention was assessed based on questionnaire feedback. Dietary nitrate significantly increased plasma and salivary nitrate/nitrite concentrations compared with placebo juice (p < 0.001), with marked variation between women. Compared with placebo, there was no overall reduction in blood pressure in the nitrate-treated group; however there was a highly significant correlation between changes in plasma nitrite concentrations and changes in diastolic blood pressure in the nitrate-treated arm only (r = -0.6481; p = 0.0042). Beetroot juice supplementation was an acceptable dietary intervention to 97% of women. This trial confirms acceptability and potential efficacy of dietary nitrate supplementation in pregnant women. Conversion of nitrate to nitrite critically involves oral bacterial nitrate reductase activities. We speculate that differences in efficacy of nitrate supplementation relate to differences in the oral microbiome, which will be investigated in future studies.

Chronic Kidney Disease and Pregnancy

Women with chronic kidney disease (CKD) are at risk for adverse pregnancy-associated outcomes, including progression of their underlying renal dysfunction, a flare of their kidney disease, and adverse pregnancy complications such as preeclampsia and preterm delivery. Earlier-stage CKD, as a rule, is a safer time to have a pregnancy, but even women with end-stage kidney disease have attempted pregnancy in recent years. As such, nephrologists need to be comfortable with pregnancy preparation and management at all stages of CKD. In this article, we review the renal physiologic response to pregnancy and the literature with respect to both expected maternal and fetal outcomes among young women at various stages of CKD, including those who attempt to conceive while on dialysis. The general management of young women with CKD and associated complications, including hypertension and proteinuria are discussed. Finally, the emotional impact these pregnancies may have on young women with a chronic disease and the potential benefits of care in a multidisciplinary environment are highlighted.

A randomized trial of ambulatory blood pressure monitoring versus clinical blood pressure measurement in the management of hypertension in pregnancy. A feasibility study

To assess the feasibility of a prospective randomised trial of ambulatory blood pressure monitoring (ABPM) versus clinic blood pressure (CBP) readings for managing pregnancy hypertension. The primary outcome measure was admission to hospital. The secondary measures were number of antenatal attendances, use of anti-hypertensive drugs and duration of hospital stay. In general, there were no statistical differences between the two groups including the primary outcome, the rate of hospital admission p=0.76. 89% of participants would undergo ABPM in future pregnancies. A randomised trial of ABPM in pregnancy using this methodology is feasible and acceptable to pregnant women.

Pregnancy physiology pattern prediction study (4P study): protocol of an observational cohort study collecting vital sign information to inform the development of an accurate centile-based obstetric early warning score

INTRODUCTION

Successive confidential enquiries into maternal deaths in the UK have identified an urgent need to develop a national early warning score (EWS) specifically for pregnant or recently pregnant women to aid more timely recognition, referral and treatment of women who are developing life-threatening complications in pregnancy or the puerperium. Although many local EWS are in use in obstetrics, most have been developed heuristically. No current obstetric EWS has defined the thresholds at which an alert should be triggered using evidence-based normal ranges, nor do they reflect the changing physiology that occurs with gestation during pregnancy.

METHODS AND ANALYSIS

An observational cohort study involving 1000 participants across three UK sites in Oxford, London and Newcastle. Pregnant women will be recruited at approximately 14 weeks' gestation and have their vital signs (heart rate, blood pressure, respiratory rate, oxygen saturation and temperature) measured at 4 to 6-week intervals during pregnancy. Vital signs recorded during labour and delivery will be extracted from hospital records. After delivery, participants will measure and record their own vital signs daily for 2 weeks. During the antenatal and postnatal periods, vital signs will be recorded on an Android tablet computer through a custom software application and transferred via mobile internet connection to a secure database. The data collected will be used to define reference ranges of vital signs across normal pregnancy, labour and the immediate postnatal period. This will inform the design of an evidence-based obstetric EWS.

ETHICS AND DISSEMINATION

The study has been approved by the NRES committee South East Coast-Brighton and Sussex (14/LO/1312) and is registered with the ISRCTN (10838017). All participants will provide written informed consent and can withdraw from the study at any point. All data collected will be managed anonymously. The findings will be disseminated in international peer-reviewed journals and through research conferences.

Trajectory of blood pressure change during pregnancy and the role of pre-gravid blood pressure: a functional data analysis approach

The study aims to examine the blood pressure (BP) trajectory during pregnancy and its association with pre-gravid BP level. In a pre-conception cohort study, newly-married women in Liuyang, China underwent pre-gravid measurements and were followed throughout the pregnancy. BP was measured at pre-conception and again throughout pregnancy. The functional principal component analysis was used to examine the trajectory of BP changes during pregnancy. A total of 1282 women with a singleton pregnancy who had both pre-conception and gestational BP measurements performed were included in the final analysis. The results showed that BP decreased significantly in early pregnancy and increased thereafter, without BP drop around 20 weeks of gestation. Pre-gravid BP level was inversely associated with the BP drop in early pregnancy, such that women with higher pre-gravid BP had greater BP drop at the beginning, while women with the lowest pre-gravid BP level demonstrated no obvious BP drop throughout the entire pregnancy.

[Methods of blood pressure measurement during pregnancy]

Hypertension during pregnancy is associated with high perinatal morbidity and mortality. The prevalence of white coat hypertension is high during pregnancy and is associated with a good prognosis and must be excluded. The definition of hypertension during pregnancy is office BP≥140/90mmHg and ≥135/85mmHg with home BP and diurnal ambulatory BP. How to use HBPM during pregnancy? To get an adapted and validated BP humeral device during pregnancy; to use it in good conditions with the "3 rules". When to use HBPM during pregnancy? To confirm the diagnosis of hypertension; to monitor BP during pregnancy and to alert the obstetrician when severe hypertension occurs; to manage BP treatment and avoid excessive treatment. HBP and ABP monitoring may be used to exclude white coat effect but HBPM must be preferred when prolonged use.

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.

Mid-trimester blood pressure drop in normal pregnancy: myth or reality?

BACKGROUND

Current dogma states that there is a mid-trimester fall in blood pressure (BP) in uncomplicated pregnancy. In the early stages of a longitudinal study of microcirculatory changes in pregnancy, we noted an absence of this mid-trimester fall.

METHOD

We prospectively studied this phenomenon in all our subsequent recruits. From a total of 326 women, 255 primigravid white women normotensive at booking and after delivery were studied. Serial BP measurements were taken under controlled conditions through to 38 weeks gestation. BP measurements by midwives were extracted from the case notes of 51 women within this cohort and analysed to validate the results. SBP progressively increased from the first trimester through to 38 weeks gestation.

RESULTS

The increase from baseline at 13 weeks was significant when compared with measurements at 22 weeks [mean difference: 2.8 mmHg; 95% (confidence interval) CI 1.9-3.7], 28 weeks (mean difference: 5.0 mmHg; 95% CI 3.5-6.5) and 36 weeks (mean difference: 7.7 mmHg; 95% CI 6.2-9.1). DBP showed a nonsignificant dip at 22 weeks (mean difference: -0.12 mmHg; 95% CI -0.92 to 0.68), a nonsignificant increase at 28 weeks (mean difference: 2.0 mmHg; 95% CI 0.80-3.2) and a significant increase at 36 weeks (mean difference: 6.0; 95% CI 4.6-7.3). In the validation cohort, the SBP (P=0.0001) and DBP showed an increasing trend (P=0.0001).

CONCLUSION

BP measured under controlled conditions showed a progressive rise in pregnancy, with no significant mid-trimester drop. The findings were replicated in the routine antenatal clinic measurements.

The midgestational maternal blood pressure decline is absent in mice lacking expression of the angiotensin II AT2 receptor

The midgestational maternal blood pressure (BP) decrease is absent in mice treated with an angiotensin II AT2 receptor blocker. We tested the hypotheses that there would be 1) no midgestational decrease in maternal systolic BP (SBP) in AT2-/- mice, and 2) a pattern of increased AT2 and/or decreased AT1a mRNA expression in tissues from normal (wild-type, WT) mice, corresponding with SBP changes. Heart, aorta, placenta and kidney tissue were obtained from WT and AT2-/- mice before pregnancy and on gestational days (Gd) 5-6, 12-13 and 18-19. AT1a and AT2 mRNA expression was quantified. SBP was measured. SBP was significantly decreased in WT Gd12-13 mice, but did not change during pregnancy in AT2-/- mice. In WT mice, aortic AT1a mRNA expression levels were significantly higher at Gd12-13 and Gd18-19 compared with before pregnancy. AT1a kidney and heart mRNA did not change during pregnancy. There were no changes in AT2 mRNA expression. There was no distinct pattern of change in AT1a expression in AT2-/mice. Placental AT1a and AT2 expression levels increased markedly between Gd12-13 and Gd18-19 in WT mice. We conclude that the AT2 receptor is essential for the midgestational SBP decline in WT mice. There is no consistent relationship between changes in tissue angiotensin II receptor mRNA expression and SBP in WT mice.

Physiological changes of pregnancy and monitoring

Advances in medical care have led to increasing numbers of complex, high-risk obstetric patients. Specialist training and a sound knowledge of normal maternal physiology are essential to optimize outcomes. One of the earliest observed changes is peripheral vasodilatation; this causes a fall in systemic vascular resistance and triggers physiological changes in the cardiovascular and renal systems, with 40-50% increases in cardiac output and glomerular filtration rates. Safety concerns over Swan Ganz catheters have driven the increasing interest in alternative techniques, such as echocardiography, thoracic bioimpedance and pulse contour analysis, although their exact roles in future obstetric high-dependency care have yet to be established. Analysis of arterial blood gases is fundamental to the management of sick patients, and correct interpretation can be aided by a systematic approach. Observation charts are almost ubiquitous in all aspects of medicine, but little evidence exists to support their use in the high-dependency setting.

Diurnal blood pressure variation in the evaluation of early onset severe pre-eclampsia

OBJECTIVE

To study the association between diurnal variation in blood pressure, the mean daily blood pressure and various complications of pregnancy in patients presenting with severe pre-eclampsia before 34 weeks' gestation.

STUDY DESIGN

Forty-four women presenting to a tertiary hospital in South Africa with severe pre-eclampsia between 28 and 34 weeks' gestation were managed expectantly for at least 8 days. We measured maternal blood pressure every 30 min with the pregnancy validated Spacelabs 90209 automated blood pressure monitor for 24h periods on alternative days. The mean 24-h diastolic blood pressure measurement, the mean diastolic blood pressure for daytime and nighttime, the day-night blood pressure difference and the night-day ratio were compared with the occurrence of abruptio placentae, gestational age at delivery, neonatal intensive care unit admission, birth weight, abnormal umbilical artery Doppler FVW and reason for delivery.

RESULTS

One hundred and seventy-six 24-h studies were analyzed. The day-night blood pressure difference decreased with increasing mean diastolic blood pressure (r=-0.323, p<0.0001). A combination of normal mean diastolic blood pressure and normal day-night blood pressure difference was associated with increased gestational age and lower caesarean section rates.

CONCLUSION

The combination of mean diastolic blood pressure and day-night blood pressure difference may be a supplementary measurement of disease severity in early onset severe pre-eclampsia and seems to be of prognostic value.

Maternal circulating endothelial progenitor cells in normal singleton and twin pregnancy

OBJECTIVE

The objective of the study was to determine the levels of circulating endothelial progenitor cells (EPCs), which are peripheral blood mononuclear cells (PBMNCs) that contribute to vascular repair in normal pregnancy.

STUDY DESIGN

The concentration of EPCs in maternal blood was measured in healthy nonpregnant women (group A, n = 8), normal singleton pregnancies (group B, n = 24), and normal twin pregnancies (group C, n = 21).

RESULTS

In group A, the mean (SD) level of EPCs was 77.0% (8.6%) adherent PBMNCs. In group B, the mean level was lower than in group A and decreased with gestation from 61.3% (14.9%) in the first trimester to 56.0% (16.2%) in the second trimester and 52.0% (8.7%) in the third trimester (P = .001). Similarly, the level of EPCs in group C was lower than in group A and decreased with gestation from 64.6% (9.6%) in the first trimester to 65.2% (12.7%) in the second trimester and 56.4% (12.6%) in the third trimester (P = .002).

CONCLUSION

Normal pregnancy is associated with a decrease in maternal circulating levels of EPCs.

A review and rationale for studying the cardiovascular effects of drinking water arsenic in women of reproductive age

Drinking water arsenic has been shown to be associated with a host of adverse health outcomes at exposure levels >300 microg of As/L. However, the results are not consistent at exposures below this level. We have reviewed selected articles that examine the effects of drinking water arsenic on cardiovascular outcomes and present a rationale for studying these effects on women of reproductive age, and also over the course of pregnancy when they would potentially be more susceptible to adverse cardiovascular and reproductive outcomes. It is only recently that reproductive effects have been linked to drinking water arsenic. However, there is a paucity of information about the cardiovascular effects of drinking water arsenic on women of reproductive age. Under the cardiovascular challenge of pregnancy, we hypothesize that women with a slightly elevated exposure to drinking water arsenic may exhibit adverse cardiovascular outcomes at higher rates than in the general population. Studying sensitive clinical and sub-clinical indicators of disease in susceptible sub-populations may yield important information about the potentially enormous burden of disease related to low-level drinking water arsenic exposure.

Reference thresholds for 24-h, diurnal, and nocturnal ambulatory blood pressure mean values in pregnancy

OBJECTIVES

Several studies have indicated that the use of the 24-h mean of blood pressure, mainly using reference thresholds derived from the general non-pregnancy practice, does not provide a proper test for diagnosis of hypertension in pregnancy. This prospective study examines previously derived reference thresholds for the 24-h, diurnal, and nocturnal mean of blood pressure as potential screening tests for the diagnosis of hypertension in pregnancy.

METHODS

We studied 235 normotensive and 168 hypertensive pregnant women, who provided 2430 blood pressure series sampled every 20 min during the day and every 30 min at night for 48 consecutive hours once every 4 weeks from the first obstetric visit until delivery. Sensitivity and specificity for each parameter are based on the comparison of the distributions of mean blood pressure values with reference thresholds previously established from an independent population of 113 pregnant women also evaluated monthly by 48-h ambulatory monitoring throughout gestation.

RESULTS

Sensitivity of mean blood pressure values, above 70% at all stages of pregnancy, was higher than that obtained from clinic blood pressure measurements, which were always below 14%. The poorest results were consistently obtained for the nocturnal mean. Sensitivity was similar for the 24-h and the diurnal mean, with values ranging from 71% for diastolic blood pressure in the first trimester of pregnancy to 93% for systolic blood pressure in the third trimester. Systolic blood pressure consistently provided better sensitivity than diastolic blood pressure at all gestational ages.

CONCLUSIONS

This prospective study on women systematically studied by 48-h ambulatory monitoring throughout gestation indicates that mean ambulatory blood pressure values provide higher sensitivity and specificity than conventional measurements. Moreover, results indicate that diagnosis of hypertension in pregnancy based on ambulatory blood pressure should be established from thresholds much lower than those currently used in clinical practice.

Maternal blood pressure in pregnancy, birth weight, and perinatal mortality in first births: prospective study

OBJECTIVE

To investigate the relation of diastolic blood pressure in pregnancy with birth weight and perinatal mortality.

DESIGN

Prospective study.

SETTING

15 maternity units in one London health region, 1988-2000.

PARTICIPANTS

210 814 first singleton births of babies weighing more than 200 g among mothers with no hypertension before 20 weeks' gestation and without proteinuria, delivering between 24 and 43 weeks' gestation.

MAIN OUTCOME MEASURES

Birth weight and perinatal mortality.

RESULTS

The mean (SD) birth weight of babies born to mothers with no hypertension before 20 weeks' gestation or proteinuria was 3282 g (545 g) and there were 1335 perinatal deaths, compared with 94 perinatal deaths among women with proteinuria or a history of hypertension. Diastolic blood pressure at booking for antenatal checks was progressively higher from weeks 34 to 40 of gestation. The birth weight of babies being delivered after 34 weeks was highest for highest recorded maternal diastolic blood pressures of between 70 and 80 mm Hg and lower for blood pressures outside this range. Both low and high diastolic blood pressures were associated with statistically significantly higher perinatal mortality. Using a linear quadratic model, 94 of 825 (11.4%) perinatal deaths could be attributed to mothers having blood pressure differing from the optimal blood pressure (82.7 mm Hg) predicted by the fitted model. Most of these excess deaths occurred with blood pressures below the optimal value.

CONCLUSIONS

Both low and high diastolic blood pressures in women during pregnancy are associated with small babies and high perinatal mortality.

Endothelial NO synthase genotype and risk of preeclampsia: a multicenter case-control study

Polymorphisms in the endothelial NO synthase (eNOS) gene have been evaluated as risk factors for preeclampsia. However, data from small studies are conflicting. We assessed whether eNOS genotypes alter the risk of preeclampsia in a population in which the incidence of this disorder is high. A total of 844 young pregnant women (322 preeclamptic and 522 controls) were recruited from 5 cities. Genotyping for the Glu298Asp, intron-4 and -786T-->C polymorphisms in the eNOS gene was conducted. Multivariate odds ratios (ORs) were obtained to estimate the association of individual polymorphisms and haplotypes with preeclampsia risk. No increase in the risk of preeclampsia for the intron-4 or -786T-->C polymorphisms was observed under any model of inheritance. In contrast, in women homozygous for the Asp298 allele, the adjusted OR for preeclampsia was 4.60 (95% confidence interval [CI], 1.73 to 12.22) compared with carriers of the Glu298 allele. After a multivariate analysis, carriage of the "Asp298-786C-4b" haplotype was also associated with increased risk of preeclampsia (OR, 2.11 [95% CI, 1.33 to 3.34]) compared with carriers of the "Glu298-786T-4b" haplotype. The eNOS Glu298Asp polymorphism and the Asp298-786C-4b haplotype are risk factors for preeclampsia.

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.

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.

Vascular adaptations to pregnancy in mice: effects on myogenic tone

The mechanisms underlying vascular adaptations in pregnancy remain to be fully elucidated. One of the contributory mechanisms for reduced vascular tone may be a reduction of myogenic tone. Myogenic tone was assessed as the difference between internal diameter in the presence and absence of external calcium at different intramural pressure steps (60-100 mmHg). Myogenic responses were reduced in resistance-sized mesenteric and main uterine arteries in late pregnant compared with nonpregnant C57BL/6J mice. In vessels from pregnant, but not nonpregnant mice, the myogenic response was enhanced by preincubation with nitric oxide (NO) synthase inhibitor N(G)-nitro-l-arginine methyl ester, was further elevated by the gap junction inhibitor 18-alpha glycyrrhetinic acid, but was unaltered by the prostaglandin H synthase inhibitor meclofenamate. Endothelium removal enhanced myogenic tone only in the vessels from pregnant animals, thus confirming the role of the endothelium in modulating myogenic tone in pregnancy. These results suggest that endothelium-derived NO as well as gap junction communications modulate myogenic tone in mouse pregnancy.

Evaluation of ambulatory and self-initiated blood pressure monitors by pregnant and postpartum women

OBJECTIVE

To investigate the acceptability of an ambulatory blood pressure (ABP) monitor (SpaceLabs 90207) and a self-initiated blood pressure monitor (Omron HEM-705CP) to pregnant women.

METHODS

Acceptability of the SpaceLabs 90207 and Omron HEM- 705CP monitors was evaluated, using a modified British Hypertension Device assessment form, by () healthy, pregnant women at <15 weeks (n = 120), 35-37 weeks (n = 81), and 5-9 weeks postpartum (n = 86); and () women with preeclampsia (n = 52).

MAIN OUTCOME MEASURES

A monitor was acceptable if a woman graded the overall impression as "good" or "very good."

RESULTS

Healthy women at <15 and 35-37 weeks' gestation and preeclamptic women reported the SpaceLabs 90207 monitor caused discomfort in 54%, 52%, and 60%, interfered with activities in 38%, 40%, and 23%, and disturbed sleep in 62%, 52% and 31%, respectively. Fewer than 12% in any group reported these problems with the Omron HEM-705CP monitor. In the 78 women who evaluated both monitors at 35-37 weeks, the SpaceLabs 90207 and Omron HEM-705CP were acceptable to 78% and 95% of healthy women, respectively (p = 0.005). Women with preeclampsia rated the Space-Labs 90207 as "bad" or "fair" (14%), "good" (58%), and "very good" (28%) compared with "bad" or "fair" (8%), "good" (28%), and "very good" (64%) for the Omron HEM-705CP monitor (p = 0.009).

CONCLUSIONS

Pregnant women found the less intensive blood pressure monitoring with the Omron HEM-705CP more acceptable than the 24-h ABP monitoring with the SpaceLabs 90207. If accurate self-initiated blood pressure devices become available, pregnant women would prefer this method of home blood pressure monitoring.

Validation up-date

With the increasing marketing of automated and semi-automated devices for the measurement of blood pressure, there is a need for potential purchasers to be able to satisfy themselves that such devices have been evaluated according to agreed criteria. Since their introduction a large number of blood pressure measuring devices have been evaluated according to one or both protocols. However, experience has demonstrated that the conditions demanded by the protocols are extremely difficult to fulfil. The European Society of Hypertension (ESH) protocol, named the International Protocol, which will be published shortly, is based on the data from 19 validation studies performed according to the AAMI and BHS protocols. Critical assessment of this data base of evidence has permitted rationalisation and simplification of validation procedures without loosing the merits of the much more complicated earlier protocols. This has been achieved by elimination of pre-validation phases, improving observer recruitment and training, minimising observer error during validation, reducing the number of subjects recruited, relaxing the range of blood pressures required and eliminating 'hopeless' devices early in the validation procedure.

Endothelial nitric oxide synthase gene polymorphism and maternal vascular adaptation to pregnancy

A common polymorphism of the endothelial NO synthase gene that predicts a Glu298Asp amino acid substitution in the mature protein has been associated with cardiovascular disorders in which NO bioactivity is impaired. However, the influence of this polymorphism on endothelial function is unknown. Healthy pregnancy is associated with enhanced endothelium-dependent, flow-mediated dilation (FMD) of the brachial artery, a response mediated by NO. In this study, we investigated the effect of the endothelial NO synthase Glu298Asp polymorphism on endothelium-dependent vasodilation in early pregnancy, making the hypothesis that any genotype-dependent differences in NO generation would be more marked during pregnancy, when the production of NO is upregulated. FMD of the brachial artery was recorded during the first trimester in 139 healthy women with normal singleton pregnancies genotyped for the Glu298Asp variant of endothelial NO synthase. Maternal FMD exhibited a codominant inverse relation with the number of Asp298 alleles (r=-0.21, P=0.01). Among homozygotes for endothelial NO synthase Asp298, FMD (7.99+/-1.46%) was significantly lower than that observed among individuals homozygous for endothelial NO synthase Glu298 (10.12+/-3.44) (P=0.002). In a backward stepwise multiple regression analysis, vessel size (P<0.0001) and Glu298Asp polymorphism (P=0.01) were significantly and independently correlated with FMD. Our findings indicate that the endothelial NO synthase Glu298Asp polymorphism is associated with differences in endothelium-dependent dilation at 12-week gestation and are the first to implicate genetic factors in the normal vascular adaptation to pregnancy. They also provide a potential mechanism linking the endothelial NO synthase polymorphism with the development of cardiovascular disorders and have implications for understanding the genetic basis of 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.