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National Collaborating Centre for Women's and Children's Health (UK). Hypertension in Pregnancy: The Management of Hypertensive Disorders During Pregnancy. London: RCOG Press; 2010 Aug. (NICE Clinical Guidelines, No. 107.)

2Development of the guideline

2.1. Hypertensive disorders of pregnancy

Hypertension during pregnancy is defined as a diastolic blood pressure of 90 mmHg or greater on two occasions more than 4 hours apart or a single diastolic blood pressure above 110 mmHg.5 Hypertensive disorders during pregnancy occur in women with pre-existing primary or secondary chronic hypertension, and in women who develop new-onset hypertension in the second half of pregnancy.

For the purposes of this guideline, the following definitions apply.

The guideline definitions for chronic hypertension, gestational hypertension and pre-eclampsia are broadly consistent with those agreed by the International Society for the Study of Hypertension in Pregnancy (ISSHP).6 The exceptions are hypertension that predates pregnancy but is not recognised before pregnancy and gestational hypertension that resolves after pregnancy, as these cannot be distinguished until the postnatal period. For the purpose of this guideline, therefore, the definition of chronic hypertension does not include new hypertension presenting after 20 weeks that does not resolve postnatally.

Although the definition of pre-eclampsia used in this guideline requires significant proteinuria, pre-eclampsia is a clinical syndrome and both clinical signs and symptoms and haematological or biochemicial abnormalities can occur in the absence of significant proteinuria.

The Guideline Development Group (GDG) has defined mild, moderate and severe hypertension to assist the development of guidance as follows:

Techniques for the measurement of blood pressure in pregnancy are described in ‘Antenatal care’ (NICE clinical guideline 62).1

Rates for chronic hypertension during pregnancy between 0.6% and 2.7% have been reported. There may be under-reporting in population datasets for this diagnosis, with the rate more likely to be nearer 2%.7 The rate for gestational hypertension is almost certainly under-reported, with rates between 4.2% and 7.9% recorded.7 Both chronic hypertension and gestational hypertension can progress to pre-eclampsia. Rates for pre-eclampsia are better known, though a range of 1.5% to 7.7% has been reported.8–13 The rate depends on the distribution of parity in the population: the rate for primigravid women is 4.1% and in women in their second pregnancy 1.7%.14 It is likely that up to 10% of pregnancies are complicated by hypertensive disorders and there is evidence that the rate may be increasing.

Hypertensive disorders during pregnancy carry risks for the woman and the baby. Although the rate of eclampsia in the UK appears to have fallen,15 hypertension in pregnancy remains one of the leading causes of maternal death in the UK, Europe and elsewhere.16;17 Detailed enquiries have examined standards of care, and substandard care (where different management might have been expected to prevent death) has been identified in the majority of cases. These failures of care have not just occurred in the critical care environment.

Hypertensive disorders during pregnancy may result in substantial maternal morbidity, and maternal death is the tip of the iceberg. A UK study reported that one-third of severe maternal morbidity was a consequence of hypertensive conditions,18 and a study conducted in the USA found that over half of admissions for acute kidney failure, one-quarter of admissions for coagulopathy and nearly one-third of admissions for ventilation or cerebrovascular disorders occurred in women with hypertensive disorders.19 A study from one region of the UK reported that 1 in 20 (5%) women with severe pre-eclampsia or eclampsia was admitted to intensive care.20

More recently, the long-term consequences for women with a diagnosis of hypertension during pregnancy have become clear, in particular chronic hypertension and an increase in lifetime cardiovascular risk.21

The standard pattern of antenatal care developed in the 1920s was largely aimed at detection of pre-eclampsia. Over recent years, the lack of good predictive tests and of preventative treatment has resulted in surveillance aimed at early detection and assessment of hypertensive disease in pregnancy, the consequences of which are poorly understood for women and the maternity service.

Hypertensive disorders also carry a risk for the baby. In the most recent UK perinatal mortality report, about 1 in 20 (5%) stillbirths in infants without congenital abnormality occurred in women with pre-eclampsia.22 While this may be an improvement from the late 1990s (7%),23 it still represents a significant burden. A similar trend in the stillbirth rate has been seen in Sweden.24 Ten percent of women with severe pre-eclampsia give birth before 34 weeks.14 The contribution of pre-eclampsia to the overall preterm birth rate is substantial: 1 in 250 (0.4%) women in their first pregnancy will give birth before 34 weeks as a consequence of pre-eclampsia14 and 8–10% of all preterm births result from hypertensive disorders.25 Half of women with severe pre-eclampsia give birth preterm.26

Small-for-gestational-age (SGA) babies (mainly because of intrauterine growth restriction (IUGR) arising from placental disease) are common, with 20–25% of preterm births and 14–19% of term births in women with pre-eclampsia being less than the tenth centile of birthweight for gestation.26

There is national guidance on the care of women with severe pre-eclampsia or eclampsia27 and on screening for hypertensive disorders during pregnancy.1 However, there has been no guidance on the assessment and care of women and their babies after a diagnosis of hypertension (including the use of antihypertensive treatment) or on maternity care for women with chronic hypertension.

This clinical guideline contains recommendations for the diagnosis and management of hypertensive disorders during pregnancy in the antenatal, intrapartum and postnatal periods. It includes recommendations for women with chronic hypertension who wish to conceive and recommendations for advice to women after a pregnancy complicated by hypertension. At its core is an assumption that recommendations and advice, including the generally poor quality of the evidence on which they are based, and the need to balance maternal and perinatal risk, will be fully discussed with women and their families.

2.2. Aim and scope of the guideline

This clinical guideline concerns the management of hypertensive disorders in pregnancy and their complications from preconception to the postnatal period. For the purpose of this guideline, ‘pregnancy’ includes the antenatal, intrapartum and postpartum (6 weeks after birth) periods.

The guideline has been developed with the aim of providing guidance in the following areas:

The following areas are specifically excluded from the guideline:

  • the detection of hypertension during pregnancy (this is covered in ‘Antenatal care’ (NICE clinical guideline 62)1
  • screening strategies for risk factor identification.

Further information about the areas covered in the guideline is available in the ‘scope’ of the guideline (reproduced in Appendix A).

2.3. For whom is the guideline intended?

This guideline is of relevance to those who work in or use the National Health Service (NHS) in England, Wales and Northern Ireland, in particular:

  • healthcare professionals involved in the care of women with hypertensive disorders during pregnancy and their newborn babies (including GPs, nurses, midwives, obstetricians, cardiology physicians and neonatal paediatricians)
  • those responsible for commissioning and planning healthcare services, including primary care trust commissioners, Health Commission Wales commissioners, and public health and trust managers
  • women with hypertensive disorders of pregnancy and their families.

A version of this guideline for women with hypertensive disorders of pregnancy and the public is available from the NICE website (www.nice.org.uk/CG107) or from NICE publications on 0845 003 7783 or email ku.gro.ecin@snoitacilbup (and quote reference N1739).

2.4. Other relevant documents

This guideline is intended to complement other existing and proposed works of relevance, including the following guidance published by NICE:

  • ‘Antenatal care’, NICE clinical guideline 621
  • ‘Intrapartum care’, NICE clinical guideline 5528
  • ‘Postnatal care’, NICE clinical guideline 3729
  • ‘Induction of labour’, NICE clinical guideline 7030
  • ‘Caesarean section’, NICE clinical guideline 1331
  • Hypertension’, NICE clinical guideline 343;4
  • ‘Diabetes in pregnancy’, NICE clinical guideline 6332
  • Obesity’, NICE clinical guideline 432
  • Chronic kidney disease’, NICE clinical guideline 7333
  • ‘Smoking cessation services’, NICE public health guidance 1034
  • ‘Maternal and child nutrition’, NICE public health guidance 1135
  • ‘How to stop smoking in pregnancy and following childbirth’, NICE public health guidance 2636
  • ‘Weight management before, during and after pregnancy’, NICE public health guidance 27.37

2.5. Who has developed the guideline?

The guideline was developed by a multi-professional and lay GDG convened by the National Collaborating Centre for Women’s and Children’s Health (NCC-WCH). Membership included:

  • four obstetricians
  • two midwives
  • an obstetric physician
  • an obstetric anaesthetist
  • a neonatal paediatrician
  • a GP
  • a pharmacist
  • two patient/carer members.

NCC-WCH staff provided methodological support for the guideline development process, undertook systematic searches, retrieved and appraised the evidence, developed health economic models, and wrote successive drafts of the guideline.

Four external advisers were appointed by the GDG to advise on anaesthesia, obstetric critical care, and methods for detection and quantification of urinary protein.

All GDG members’ and external advisers’ potential and actual conflicts of interest were recorded on declaration forms provided by NICE (summarised in Appendix B). None of the interests declared by GDG members constituted a material conflict of interest that would influence recommendations developed by the GDG.

Organisations with interests in the management of hypertensive disorders during pregnancy and their complications from preconception to the postnatal period were encouraged to register as stakeholders for the guideline. Registered stakeholders were consulted throughout the guideline development process. The types of organisations eligible to register as stakeholders included:

  • national patient and carer organisations that directly or indirectly represent interests of women with hypertensive disorders of pregnancy and their families
  • national organisations that represent healthcare professionals who provide services for women with hypertensive disorders of pregnancy
  • companies that manufacture preparations and/or products used in the management of hypertensive disorders during pregnancy
  • providers and commissioners of health services in England, Wales and Northern Ireland
  • statutory organisations such as the Department of Health and the Welsh Assembly Government
  • research organisations that have undertaken nationally recognised research in relation to the topics covered in the guideline.

A list of registered stakeholder organisations for this guideline is presented in Appendix C.

2.6. Guideline development methodology

This guideline was commissioned by NICE and developed in accordance with the process outlined in successive editions of ‘The guidelines manual’ (see www.nice.org.uk/guidelinesmanual). Table 2.1 summarises the key stages of the process and which version of ‘The guidelines manual’ was followed at each stage. In accordance with NICE’s Equality Scheme (see www.nice.org.uk/aboutnice/howwework/NICEEqualityScheme.jsp), ethnic and cultural considerations and factors relating to disabilities were considered by the GDG at every stage of the process and addressed specifically in individual recommendations where relevant.

Table 2.1. Stages in the NICE guideline development process and versions of the ‘The guidelines manual’ followed at each stage.

Table 2.1

Stages in the NICE guideline development process and versions of the ‘The guidelines manual’ followed at each stage.

Developing clinical questions and identifying evidence

The GDG formulated clinical questions based on the scope (see Appendix D). These formed the starting point for subsequent evidence reviews. Relevant published evidence to answer the clinical questions was identified by applying systematic search strategies (see Appendix E) to the following databases: Medline (1950 onwards), Embase (1980 onwards), Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 onwards), and three Cochrane databases (Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and the Database of Abstracts of Reviews of Effects). Searches to identify economic studies were undertaken using the above databases and the NHS Economic Evaluation Database (NHS EED). None of the searches was limited by date or language of publication (although publications in languages other than English were not reviewed). Generic and specially developed search filters were used to identify particular study designs, such as randomised controlled trials (RCTs). There was no systematic attempt to search grey literature (conferences, abstracts, theses and unpublished trials), nor was hand searching of journals not indexed on the databases undertaken.

Towards the end of the guideline development process, the searches were updated and reexecuted to include evidence published and indexed in the databases by 20 May 2009.

Reviewing and grading evidence

Evidence relating to clinical effectiveness was reviewed and graded using the hierarchical system presented in Table 2.2. This system reflects the susceptibility to bias inherent in particular study designs.

Table 2.2. Levels of evidence for intervention studies.

Table 2.2

Levels of evidence for intervention studies.

The type of clinical question dictates the highest level of evidence that may be sought. In assessing the quality of evidence, each study was assigned a quality rating coded as ‘++’, ‘+’ or ‘−’. For issues of therapy or treatment, the highest possible evidence level (EL) is a well-conducted systematic review or meta-analysis of RCTs (EL = 1++) or an individual RCT (EL = 1+). Studies of poor quality were rated as ‘−’. Studies rated as ‘−’ should not be used as a basis for making a recommendation, but they may be used to inform recommendations. For issues of prognosis, the highest possible level of evidence is a cohort study (EL = 2).

For each clinical question, the highest available level of evidence was sought. Where appropriate, for example if a systematic review with or without a meta-analysis or an RCT was identified to answer a question, studies of a weaker design were not considered. Where such studies were not identified, other appropriate experimental or observational studies were sought. For diagnostic tests, test evaluation studies examining the performance of the test were used if the effectiveness (accuracy) of the test was required, but where an evaluation of the effectiveness of the test in the clinical management of patients (women or their babies) and the outcome of disease was required, evidence from RCTs or cohort studies was optimal. For studies evaluating the accuracy of a diagnostic test, sensitivity, specificity, positive predictive values (PPVs) and negative predictive values (NPVs) were calculated or quoted where possible (see Table 2.3). Likelihood ratios (LRs) were also quoted where reported.

Table 2.3. ‘2 × 2’ table for calculation of diagnostic accuracy parameters.

Table 2.3

‘2 × 2’ table for calculation of diagnostic accuracy parameters.

The hierarchical system described above covers studies of treatment effectiveness. However, it is less appropriate for studies reporting accuracy of diagnostic tests. In the absence of a validated ranking system for this type of test, NICE has developed a hierarchy of evidence that takes into account various factors likely to affect the validity of such studies (see Table 2.4).

Table 2.4. Levels of evidence for studies of the accuracy of diagnostic tests.

Table 2.4

Levels of evidence for studies of the accuracy of diagnostic tests.

Some studies were excluded from the reviews after obtaining copies of then because they did not meet inclusion criteria specified by the GDG (see Appendix F). Clinical evidence from included studies was extracted into evidence tables for each question (see Appendix G), and a brief summary of each study was included in the guideline text. Where possible, dichotomous outcomes are presented as relative risks (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs), and continuous outcomes are presented as mean differences with 95% CIs or standard deviations (SDs).

The body of evidence identified for each clinical question was synthesised qualitatively in clinical evidence statements. Quantitative synthesis (meta-analysis) was not undertaken for this guideline because there were no clinical questions for which sufficient numbers of similar studies were identified to merit such analysis.

Incorporating health economics

The aims of the health economic input to the guideline were to inform the GDG of potential economic issues relating to the management of hypertensive disorders during pregnancy and to ensure that recommendations represented a cost-effective use of healthcare resources. Health economic evaluations aim to integrate data on benefits (ideally in terms of quality-adjusted life years; QALYs), harms and costs of various care options.

The GDG prioritised a number of clinical questions where it was thought that economic considerations would be particularly important in formulating recommendations. Systematic searches for published economic evidence were undertaken for these questions. For economic evaluations, no standard system of grading the quality of evidence exists and included papers were assessed using a quality assessment checklist based on good practice in economic evaluation.38 Reviews of the (very limited) relevant published economic literature are presented alongside the clinical effectiveness reviews or as part of appendices detailing original economic analyses (see below).

Health economic considerations were aided by original economic analysis undertaken as part of the development process. For this guideline, the areas prioritised for economic analysis were as follows:

GDG interpretation of the evidence and creating recommendations

For each clinical question, recommendations for clinical care were derived using, and linked explicitly to, the evidence that supported them. In the first instance, informal consensus methods were used by the GDG to agree clinical and, where appropriate, cost-effectiveness evidence statements. Statements summarising the GDG’s interpretation of the evidence and any extrapolation from the evidence used to form recommendations were also prepared to ensure transparency in the decision-making process.

In areas where no substantial clinical research evidence was identified, the GDG considered other evidence-based guidelines and consensus statements or used their collective experience to identify good practice. The health economics justification in areas of the guideline where the use of NHS resources (interventions) was considered was based on GDG consensus in relation to the likely cost-effectiveness implications of the recommendations. The GDG also identified areas where evidence to answer their clinical questions was lacking and used this information to formulate recommendations for future research.

Towards the end of the guideline development process, formal consensus methods were used to consider all the clinical care recommendations and research recommendations that had been drafted previously. The GDG identified ten ‘key priorities for implementation’ (key recommendations) and five high-priority research recommendations. The key priorities for implementation were those recommendations likely to have the biggest impact on patient care and patient outcomes in the NHS as a whole; they were selected using a variant of the nominal group technique (see the NICE guidelines manual). The priority research recommendations were selected in a similar way.

Stakeholder involvement in the guideline development process

Registered stakeholder organisations were invited to comment on the draft scope of the guideline and on the draft guideline. Stakeholder organisations were also invited to undertake a pre-publication check of the final guideline to identify factual inaccuracies. The GDG carefully considered and responded to all comments received from stakeholder organisations. The comments and responses, which were reviewed independently for NICE by a Guidelines Review Panel, are published on the NICE website.

2.7. Specific considerations for this guideline

Where the evidence supported it, the GDG made separate recommendations for women with chronic hypertension, gestational hypertension and pre-eclampsia.

For this guideline, the effectiveness of interventions was assessed against the following maternal, neonatal and infant outcomes:

  • maternal outcomes:

    maternal death

    pre-eclampsia

    severe pre-eclampsia, eclampsia and HELLP syndrome

    maternal complications (CVA, cerebral haemorrhage, myocardial infarction, kidney failure, placental abruption and pulmonary oedema)

    admission to a high-dependency unit (HDU) or intensive care unit (ICU)

    need for antihypertensive medications

    maternal QALYs

  • neonatal and infant outcomes:

    perinatal mortality, neonatal death and fetal death

    neonatal complications (hypoglycaemia, hypothermia, hypotension, feeding difficulties, jaundice and neonatal bradycardia)

    admission to a neonatal intensive care unit (NICU)

    SGA and IUGR

    preterm birth before 34 weeks

    preterm birth (before 37 weeks)

    short-term evidence of hypoxia (cord pH, hypoxic ischaemic encephalopathy, need for resuscitation at birth in a term baby)

    long-term complications (neurodevelopment)

    neonatal QALYs.

2.8. Schedule for updating the guideline

Clinical guidelines commissioned by NICE are published with a review date 3 years from the date of publication. Reviewing may begin before 3 years have elapsed if significant evidence that affects guideline recommendations is identified sooner.

In this revised reprint, the wording of the recommendations to avoid the use of angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and chlorothiazide have been revised (see Sections 1.1, 1.2 and 4.2.1). The care pathway has also been revised to reflect the changes to the recommendations (see Section 1.5).

Copyright © 2011, Royal College of Obstetricians and Gynaecologists.

No part of this publication may be reproduced, stored or transmitted in any form or by any means, without the prior written permission of the publisher or, in the case of reprographic reproduction, in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK [www.cla.co.uk]. Enquiries concerning reproduction outside the terms stated here should be sent to the publisher at the UK address printed on this page.

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore for general use.

Cover of Hypertension in Pregnancy
Hypertension in Pregnancy: The Management of Hypertensive Disorders During Pregnancy.
NICE Clinical Guidelines, No. 107.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2010 Aug.

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