Ambulatory versus conventional methods for monitoring blood pressure during pregnancy.

Objective

To assess whether the use of ambulatory blood pressure monitoring during pregnancy improves subsequent maternal and feto-neonatal outcomes, women-newborn quality of life or use of health service resources, compared with conventional (clinic) blood pressure measurements. These effects will be assessed for the following subgroups: (1) Women at low or average risk of hypertensive disorders of pregnancy (unselected). (2) Women defined as high risk of hypertensive disorders of pregnancy. (3) Women with hypertension without other signs of pre-eclampsia. (4) Women with established pre-eclampsia.

Criteria for considering studies for this review

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2005), MEDLINE (January 2005), LILACS (July 2001) and EMBASE (April 2005) were searched. We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 14 March 2011 and added the results to the awaiting classification section.

Selection criteria

All randomised trials comparing ambulatory blood pressure monitoring versus conventional (clinic) blood pressure monitoring in pregnancy. Quasi-random designs will be excluded.

Data collection and analysis

Two reviewers evaluated all potentially relevant articles, examined each study for possible inclusion and assessed the methodological quality using the Cochrane guidelines.

Main results

No trials included.

Authors' conclusions

There is no randomised controlled trial evidence to support the use of ambulatory blood pressure monitoring during pregnancy. Randomized trials with adequate design and sample sizes are needed to evaluate the possible advantages and risks of ambulatory blood pressure monitoring during pregnancy, in particular in hypertensive pregnant women. These trials should evaluate not only clinical outcomes, but also use of health care resources and women's views.

Plain language summary

Not enough evidence to show whether wearing a blood pressure monitoring device for 24 hours during pregnancy is better at detecting hypertension than clinic tests.

High blood pressure (hypertension), when associated with protein in the urine (pre-eclampsia), can lead to serious complications during pregnancy. Measuring and monitoring blood pressure has therefore been a central feature of pregnancy care. However, the value of one-off measurements at a clinic visit have been questioned. Blood pressure measurement devices have been developed which the woman wears during her normal activities. These take several measurements, usually over a 24-hour period (ambulatory blood pressure monitoring). The review of trials found there was no evidence to assess the effects of ambulatory blood pressure monitoring during pregnancy.

Last assessed as up-to-date: 30 January 2005.

Background

Hypertensive disorders are among the most common medical complications of pregnancy and a leading cause of maternal and perinatal morbidity and mortality world-wide ( Duley 1992 ; Kaunitz 1985 ). Pregnancy-induced hypertension alone carries little added risk for mother or fetus ( Page 1976 ; Conde-Agudelo 1993 ). However, when high blood pressure is associated with proteinuria, a condition known as pre-eclampsia, there are increased risks for the mother and her baby.

When severe, this disease can lead to serious maternal problems including convulsions, cerebral (brain) haemorrhage, separation of the placenta from the uterine wall (abruptio placentae), clotting dysfunctions that cause widespread bleeding (disseminated intravascular coagulopathy), accumulation of fluid in the pulmonary tissues (pulmonary edema), renal (kidney) failure, liver haemorrhage and even death. The risks for the fetus include severe growth retardation (fetus grows at a slower rate than expected), asphyxia, preterm birth and death ( MacGillivray 1969 ; Naeye 1979 ; Sibai 1996 ). Women with chronic underlying hypertension that precedes pregnancy are at increased risk of developing pre-eclampsia, abruptio placentae and poor perinatal outcome ( Sibai 1991 ).

A key question is whether a combination of screening methods, prophylactic measures and active interventions in the form of rest or medication will prevent progression of pregnancy induced hypertension or chronic hypertension to more severe forms of the disease and improve maternal and perinatal outcomes ( Villar 1997 ). Blood pressure measurement plays a central role in these strategies, and is almost always measured whenever pregnant women attend antenatal clinics. Despite its widespread use, conventional blood-pressure readings are prone to inaccuracy due to observer and device error, and evidence suggests that health professionals involved in antenatal care fail to take even the most basic precautions to lower error ( Brown 1992 ; Perry 1991 ). Furthermore, blood pressure measurements are affected by the stress response associated with a hospital setting, the so called white-coat hypertension, which may occur in nearly 30% of pregnant women ( Bellomo 1999 ). Its recognition is important, so that pregnant women are not admitted to hospital or given antihypertensive drugs unnecessarily or excessively. As a consequence attention has focused on methods of measurement that provide profiles of blood pressure behaviour rather than relying on isolated measurements under circumstances that may in themselves influence the level of blood pressure recorded ( O'Brien 2001 ).

Alternatives to conventional blood pressure measures at the clinic includes the use of automated devices for self measurement of blood pressure at home. In home blood pressure monitoring programs patients are trained to use the device and interpret readings in order to contact their physician/midwife if abnormal readings are obtained, or as an alternative readings are sent to a central facility (i.e. via telephone lines) where they are evaluated by a health care professional ( O'Brien 2001b ).

These strategies can be extended to the use of a portable automatic device that can perform repeated measurements over a predetermined length of time (typically 24 hours) while women follow their normal daily routine ( Greer 1993 ). In these devices inflation and deflation of the cuff is automatic, and blood pressure is usually determined using either brachial artery microphones to detect Korotkoff sounds or cuff oscillometry to detect cuff pressure oscillations. In this strategy, usually referred as ambulatory blood pressure monitoring (ABPM), women are instructed on the correct use of the monitor at the clinic, and wear the device. Then, women leave the clinic and follow a normal daily routine. Periodically, the monitor takes a measurement and stores the results. The measurement frequency can be varied, but it is usually between 20 and 30 minutes while awake and 30 and 60 minutes while sleeping. Women are encouraged to keep diaries so that the cause of sudden changes in blood pressure can be evaluated. The units function poorly during strenuous activity and work best if women slow or stop moving during readings. When the monitoring period is over, women return to the clinic and data are downloaded from the monitor to a computer for analysis. Many statistical techniques exist to evaluate ambulatory records, including plotting time of day versus blood pressure, 24 hour mean, daytime mean and night time mean blood pressure.

Twenty-four-hour ambulatory blood pressure monitoring can show alteration in the normal (circadian) pattern of blood pressure variation, a feature particularly relevant in pre-eclampsia, as these women showed an impairment in the night-time fall in blood pressure present in both the normotensive and gestational hypertensive patients ( Higgins 1997 ). Several studies have evaluated different aspects of ABPM during pregnancy, and devices have been successfully validated and used to generate normal ranges throughout gestation ( Higgins 2001 ). Ambulatory blood pressure correlates better with proteinuria than does conventional sphygmomanometry.; it is a better predictor of hypertensive complications, and women diagnosed by the technique as having hypertension have infants with lower birth weight than normotensive women ( O'Brien 2001 ). Moreover, women with white coat hypertension have a higher incidence of cesarean delivery than normotensive women, suggesting that if ambulatory rather than clinic blood pressure measurement was used in the decision-making processes, caesarean delivery might be avoided ( Bellomo 1999 ). On the other hand, evidence also suggests that ABPM is not useful as an early predictor of pre-eclampsia and that the technique is inaccurate in women with established pre-eclampsia, with a potential large underestimation of the true blood pressure ( Higgins 1997 ; Natarajan 1999 ). In non-pregnant subjects, there is evidence from a randomised trial suggesting that adjustment of antihypertensive treatment based on ABP monitoring instead of conventional sphygmomanometry may lead to less intensive drug treatment with preservation of BP control, general well-being, and inhibition of left ventricular enlargement ( Staessen 1997 ).

New generation devices are small, about the size of a personal cassette player, light, and quiet. When evaluated in general practice, 49% of women reported some interference with normal activity and 76% reported some disruption of sleep ( Carney 1997 ). Bed partners may also complain of interrupted sleep. There have been some reports of adverse events associated with ABPM, in particular redness of the arm, petechial skin lesions, and compartment syndrome, although the overall rate of complications seems to be low ( Tapolyai 2001 ). Women may be able to start or stop recordings and read the displayed results if they wish. This information may improve women's self confidence on one hand, but increase anxiety levels on the other hand. These issues need to be taken into account when evaluating the implementation of this diagnostic strategy.

The implementation into clinical practice of a screening or diagnostic test must lead to improved maternal and feto-neonatal clinical outcomes, quality of life or use of health service resources. Unfortunately this is not always the case, even for widely accepted procedures ( Lancet 1998 ). A pre-requisite, other than the test ability to predict or confirm disease, involves the availability of interventions that must favourably alter the natural history of the condition, not simply by advancing the time at which diagnosis occurs, but by improving survival, function, or quality of life. Claims for benefit must be supported by experimental evidence from randomised controlled clinical trials ( Sackett 1991 ).

The aims of this review are (i) to identify as many of the published and unpublished randomised controlled trials of ABPM as possible and (ii) to estimate the benefits and hazards of incorporating ABPM in the management of pregnant women.

Another review will compare self (home) blood pressure monitoring versus conventional (clinic) blood pressure monitoring and ABPM.

Objectives

To assess whether the use of ambulatory blood pressure monitoring during pregnancy improves subsequent maternal and feto-neonatal outcomes, women-newborn quality of life or use of health service resources, compared with conventional (clinic) blood pressure measurements.

These effects will be assessed for the following subgroups:

Women at low or average risk of hypertensive disorders of pregnancy (unselected).

Women defined as high risk of hypertensive disorders of pregnancy. These will include women selected by the trial authors on the basis of an increased risk of hypertensive disorders of pregnancy (eg women with previous pre-eclampsia, women with increased sensitivity to angiotensin II, women with a positive roll-over test, women with pre-existing hypertension, etc).

Women with hypertension without other signs of pre-eclampsia.

Women with established pre-eclampsia.

Methods of the review

Criteria for considering studies for this review

Types of studies

All randomised trials comparing ambulatory blood pressure monitoring versus conventional (clinic) blood pressure monitoring in pregnancy. Quasi-random designs will be excluded.

Types of participants

Pregnant women.

The effects of the intervention will be assessed in the following subgroups:

Women at low or average risk of hypertensive disorders of pregnancy (unselected).

Women defined as high risk of hypertensive disorders of pregnancy. These will include women selected by the trial authors on the basis of an increased risk of hypertensive disorders of pregnancy (eg women with previous pre-eclampsia, women with increased sensitivity to angiotensin II, women with a positive roll-over test, women with pre-existing hypertension, etc).

Women with hypertension without other signs of pre-eclampsia.

Women with established pre-eclampsia.

Types of intervention

Trials of ambulatory blood pressure monitoring, using automated devices that provide a large number of blood pressure measurements over a period of time, usually a 24-hour period, compared with conventional (clinic) blood pressure measurements.

Types of outcome measures

Maternal outcomes: death, pre-eclampsia, eclampsia, need for elective delivery, cesarean section, haemorrhage, and other measures of serious maternal morbidity. Child outcomes: stillbirth, neonatal mortality, perinatal mortality, gestational age at birth, low birth weight, small for gestational age, low Apgar score, admission to neonatal intensive care unit, infant and child development.

Use of health service resources. For the woman, antenatal hospital admission, visits to day care units, cesarean section, use of intensive care, ventilation and dialysis. For the infant, admission to special care/intensive care nursery, duration of mechanical ventilation, length of stay in hospital, as well as development and special needs after discharge.

Measures of maternal quality of life. Women's views, measures of anxiety levels and self-confidence.

Search methods for identification of studies

Electronic searches

We contact the Trials Search Co-ordinator to search the Cochrane Pregnancy and Childbirth Group Trials Register (January 2005). We updated this search on 14 March 2011 and added the results to Studies awaiting classification.

The Cochrane Pregnancy and Childbirth Group’s Trials Register is maintained by the Trials Search Co-ordinator and contains trials identified from:

-quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);

-weekly searches of MEDLINE;

-weekly searches of EMBASE;

-handsearches of 30 journals and the proceedings of major conferences;

-weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Details of the search strategies for CENTRAL, MEDLINE and EMBASE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the ‘Specialized Register’ section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described above are each assigned to a review topic (or topics). The Trials Search Co-ordinator searches the register for each review using the topic list rather than keywords.

In addition, we searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2005), MEDLINE (January 2005), EMBASE (April 2005) and LILACS in July 2001.

The general strategy in Appendix 1 was used for MEDLINE, and modified according to the search engine characteristics when searching the other databases. Reference Manager (Researchsoft, version 9.0) software was used to reproduce a similar search strategy in all the databases.

Data collection and analysis

Two reviewers evaluated the titles and abstracts found during the literature searches, and we photocopied all potentially relevant articles. Two reviewers then independently examined each study for possible inclusion and assessed the methodological quality using the Cochrane guidelines. We focused on the method of randomization, the use of allocation concealment, the use of blinding, the assessment of outcomes and exclusion of participants after randomization.

Methodological quality

Results

Description of studies

There are no randomized trials which fit the inclusion criteria. (Three reports from an updated search in March 2011 have been added to Studies awaiting classification.)

Risk of bias in included studies

No trials included.

Effects of interventions

Not applicable.

Discussion

There are currently no randomised trials which evaluate ambulatory blood pressure monitoring during pregnancy. Given the observational data suggesting that ambulatory blood pressure monitoring (ABPM) can enhance assessment of blood pressure in pregnancy, and experimental data in non-pregnant subjects showing that hypertensive patients monitored with ABPM might have better outcomes ( Staessen 1997 ), there is a clear need for randomised trials of ABPM compared with conventional blood-pressure measurement in pregnancy, and in particular in hypertensive pregnant women. There is no evidence from randomised controlled trials to support the use of ambulatory blood pressure monitoring during pregnancy.

Authors' conclusions

Implications for practice

There is no randomised controlled trial evidence to support the use of ambulatory blood pressure monitoring during pregnancy.

Implications for research

Randomised trials with adequate design and sample sizes are needed to evaluate the possible advantages and risks of ambulatory blood pressure monitoring during pregnancy, in particular in hypertensive pregnant women. These trials should evaluate not only clinical outcomes, but also women's views and use of health care resources.

[Note: The three citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

Acknowledgements

We wish to thank Sonja Henderson (Review Group Co-ordinator of the Cochrane Pregnancy and Childbirth Group, Liverpool) for her assistance and support during the preparation of this review.

Additional references

Bellomo 1999

Bellomo G, Narducci PL, Rondoni F, Pastorelli G, Stangoni G, Angeli G. Prognostic value of 24-hour blood pressure in pregnancy. JAMA 1999;282:1447-52.

Brown 1992

Brown MA, Simpson JM. Diversity of blood pressure recording during pregnancy: implications for the hypertensive disorders. Medical Journal of Australia 1992;156:306-8.

Carney 1997

Carney S. 24-hour blood pressure monitoring: what are the benefits?. Australian Prescriber 1997;20:18-20.

Conde-Agudelo 1993

Conde-Agudelo A, Belizan JM, Lede R, Bergel EF. What does an elevated mean arterial pressure in the second half of pregnancy predict--gestational hypertension or preeclampsia?. American Journal of Obstetrics and Gynecology 1993;169:509-14.

Duley 1992

Duley L. Maternal mortality associated with hypertensive disorders of pregnancy in Africa, Asia, Latin America and the Caribbean. British Journal of Obstetrics and Gynaecology 1992;99:547-53.

Greer 1993

Greer IA. Ambulatory blood pressure in pregnancy: measurements and machines. British Journal of Obstetrics and Gynaecology 1993;100:887-9.

Higgins 1997

Higgins JR, Walshe JJ, Hallingan A, O'Brien E, Conroy R, Darling MR. Can 24-hours ambulatory blood pressure measurement predict the development of hypertension in primigravidae?. British Journal of Obstetrics and Gynaecology 1997;105:1177-84.

Higgins 2001

Higgins JR, Swiet M. Blood-pressure measurement and classification in pregnancy. Lancet 2001;357:131-5.

Kaunitz 1985

Kaunitz AM, Hughes JM, Grimes DA, Smith JC, Rochat RW, Kafrissen ME. Causes of maternal mortality in the United States. Obstetrics and Gynecology 1985;65:605-12.

Lancet 1998

Anonymous . The screening muddle. Lancet [letter; comment] 1998;351:459-.

MacGillivray 1969

MacGillivray I, Rose GA, Rowe B. Blood pressure survey in pregnancy. Clinical Science 1969;37:395-407.

Naeye 1979

Naeye RL, Friedman EA. Causes of perinatal death associated with gestational hypertension and proteinuria. American Journal of Obstetrics and Gynecology 1979;133:8-10.

Natarajan 1999

Natarajan P, Shennan AH, Penny J, Halligan AW, Swiet M, Anthony J. Comparison of auscultatory and oscillometric automated blood pressure monitors in the setting of preeclampsia. American Journal of Obstetrics and Gynecology 1999;181:1203-10.

O'Brien 2001

O'Brien E, Beevers G, Lip GY. ABC of hypertension. Blood pressure measurement. Part III-automated sphygmomanometry: ambulatory blood pressure measurement. BMJ 2001;322:1110-4.

O'Brien 2001b

O'Brien E, Beevers G, Lip GY. ABC of hypertension: Blood pressure measurement. Part IV-automated sphygmomanometry: self blood pressure measurement. BMJ 2001;322:1167-70.

Page 1976

Page EW, Christianson R. The impact of mean arterial pressure in the middle trimester upon the outcome of pregnancy. American Journal of Obstetrics and Gynecology 1976;125:740-6.

Perry 1991

Perry IJ, Wilkinson LS, Shiton RA, Beevers DG. Conflicting views on the measurement of blood pressure in pregnancy. British Journal of Obstetrics and Gynaecology 1991;98:241-3.

Sackett 1991

Sackett DL, Haynes RB, Gordon HG, Tugwell P. In: Clinical Epidemiology: a basic science for clinical medicine Boston: Little Brown and Company, 1991:-.

Sibai 1991

Sibai BM. Diagnosis and management of chronic hypertension in pregnancy. Obstetrics and Gynecology 1991;78:451-61.

Sibai 1996

Sibai BM. Treatment of hypertension in pregnant women. New England Journal of Medicine 1996;335:257-65.

Staessen 1997

Staessen JA, Byttebier G, Buntinx F, Celis H, O'Brien ET, Fagard R. Antihypertensive treatment based on conventional or ambulatory blood pressure measurement. A randomized controlled trial. Ambulatory Blood Pressure Monitoring and Treatment of Hypertension Investigators. JAMA 1997;278:1065-72.

Tapolyai 2001

Tapolyai M, Udvari-Nagy S, Schede-Don K. The rate of complications of 24-hour ambulatory blood pressure monitoring (ABPM) is low. American Journal of Hypertension 2001;14:487-8.

Villar 1997

Villar J, Bergsjo P. Scientific basis for the content of routine antenatal care. I. Philosophy, recent studies, and power to eliminate or alleviate adverse maternal outcomes. Acta Obstetricia et Gynecologica Scandinavica 1997;76:1-14.

Cover sheet

Comments and criticisms

Thornton, 9 February 2011. Summary of comments and criticisms

The authors appear to have missed this trial, by me!

Ross-McGill H, Hewison J, Hirst J, Dowswell T, Holt A, Brunskill P, Thornton JG. (2000) Antenatal home blood pressure monitoring; a pilot trial. Br J Obstet Gynaecol 107:217-221.

Surely it should be included?

[Feedback from Jim Thornton, February 2011]

Reviewer's reply

Contributors to comment

Response from Eduardo Bergel, February 2011

Keywords

Female; Humans; Pregnancy; Blood Pressure Monitoring, Ambulatory [*methods] ; Hypertension [*physiopathology] ; Pre-Eclampsia [physiopathology] ; Pregnancy Complications, Cardiovascular [*physiopathology]

History

Protocol first published: Issue 4, 1998
Review first published: Issue 2, 2002