Guidance

Appendix B: Summary of the methods used to develop this guidance

Appendix B: Summary of the methods used to develop this guidance

Introduction

The reviews and economic analyses include full details of the methods used to select the evidence (including search strategies), assess its quality and summarise it.

The minutes of the PHIAC meetings provide further detail about the Committee's interpretation of the evidence and development of the recommendations.

All supporting documents are listed in appendix E.

Key questions

The key questions were established as part of the scope. (Weight management before and during pregnancy and weight management after childbirth were scoped separately, but have now been amalgamated into one piece of guidance.) They formed the starting point for the reviews of evidence and were used by PHIAC to help develop the recommendations.

The overarching questions were:

  • What is the effectiveness and cost effectiveness of weight management interventions before and during pregnancy?

  • What are the most effective and cost-effective interventions for managing women's weight after childbirth?

The subsidiary questions were:

  • What types of dietary interventions and physical activity interventions are most effective and cost effective for weight management in women planning a pregnancy? Do they have any adverse effects?

  • What are the most effective and cost-effective ways of measuring and monitoring weight gain in pregnancy? Are there any adverse effects?

  • What are the views, perceptions and beliefs of health professionals, women actively planning a pregnancy, pregnant women, their partners and families about diet, physical activity and weight management in pregnancy and before pregnancy?

  • What internal and external factors influence the effectiveness of the intervention (such as content, delivery, setting, who is delivering the intervention, intensity, duration and target setting)?

  • What are the most effective and cost-effective dietary interventions for helping mothers, including breastfeeding mothers, achieve and maintain a healthy weight after childbirth?

  • What are the most effective and cost-effective physical activity interventions for helping mothers, including breastfeeding mothers, achieve and maintain a healthy weight after childbirth?

  • What are the most effective and cost effective interventions for helping mothers to avoid gaining more weight with each successive pregnancy?

These questions were made more specific for the reviews (see reviews for further details).

Reviewing the evidence of effectiveness

Two reviews of effectiveness were conducted.

Identifying the evidence

The following databases were searched for all types of evidence (from 1990–2008):

  • ASSIA (Applied Social Science Index and Abstracts)

  • British Nursing Index

  • CINAHL (Cumulative Index of Nursing and Allied Health Literature)

  • Cochrane Central Register of Controlled Trials

  • Cochrane Database of Systematic Reviews

  • DARE (Database of Abstracts of Reviews of Effectiveness)

  • Econlit

  • EMBASE

  • HTA (Health Technology Assessment)

  • Maternity and Infant Care

  • MEDLINE

  • NHS EED (NHS Economic Evaluation Database)

  • PyscINFO

  • Science Citation Index

  • Social Science Citation Index

A search was also conducted of the following websites:

Further details of the databases, search terms and strategies are included in the reviews.

Selection criteria

Studies were included in effectiveness review one if they involved:

  • pregnant women who were expecting a single baby

  • women seeking preconception advice

  • women who were actively planning a pregnancy

  • women in the above groups who had a history of (or who developed) impaired glucose tolerance or gestational diabetes.

Studies were excluded if they:

  • were not published in English

  • were conducted in non-OECD (Organisation for Economic Cooperation and Development) countries

  • involved pregnant women expecting more than one baby

  • involved pregnant women who were underweight (BMI <18.5 kg/m2)

  • involved pregnant women who had been diagnosed with pre-existing diabetes (type 1 and 2).

Studies were included in effectiveness review two if they involved women with a BMI greater than 18.5 kg/m² up to 2 years following the birth of their baby.

Studies were excluded if they involved:

  • women who had been diagnosed with, or who were receiving clinical treatment for, an existing condition such as type 1 or type 2 diabetes

  • women who had been diagnosed with postnatal depression

  • women who were underweight (BMI <18.5 kg/m²) after childbirth

  • women who had given birth more than 2 years before

  • clinical interventions (such as surgery or drug treatment) or complementary therapies (for example, hypnotherapy or acupuncture) to treat obesity.

Studies were also excluded if they were:

  • not published in English

  • conducted in non-OECD (Organisation for Economic Cooperation and Development) countries.

Quality appraisal

Included papers were assessed for methodological rigour and quality using the NICE methodology checklist, as set out in the NICE technical manual 'Methods for the development of NICE public health guidance' (see appendix E). Each study was graded (++, +, –) to reflect the risk of potential bias arising from its design and execution.

Study quality

++ All or most of the methodology checklist criteria have been fulfilled. Where they have not been fulfilled, the conclusions are thought very unlikely to alter.

+ Some of the methodology checklist criteria have been fulfilled. Those criteria that have not been fulfilled or not adequately described are thought unlikely to alter the conclusions.

– Few or no methodology checklist criteria have been fulfilled. The conclusions of the study are thought likely or very likely to alter.

The 'Newcastle Ottawa' scale was used in effectiveness review one to assess the quality of cohort and case–control studies. Included studies were scored as follows to indicate the risk of bias:

++ Very low risk.

+ Low risk.

– High risk.

u Unclear.

Summarising the evidence and making evidence statements

The review data was summarised in evidence tables (see full reviews).

The findings from the reviews were synthesised and used as the basis for a number of evidence statements relating to each key question. The evidence statements were prepared by the public health collaborating centre (see appendix A). The statements reflect its judgement of the strength (quantity, type and quality) of evidence and its applicability to the populations and settings in the scope.

Cost effectiveness

For effectiveness review one, the economic analysis consisted of a cost-effectiveness analysis.

For effectiveness review two, the economic analysis consisted of a review of economic evaluations and a cost-effectiveness analysis.

Economic review

For the review of economic evaluations, studies were identified by searching EconLit and NHS EED during August 2009. Targeted searches were also undertaken where additional information was required.

Studies were included if they were cost-effectiveness, cost-benefit or cost-minimisation analyses of:

  • dietary or physical activity interventions to help manage the weight of postnatal women

  • any dietary or physical activity intervention following pregnancy that may impact on the woman's weight.

Studies were excluded if they:

  • were not published in English

  • involved pharmacological interventions, surgery or complementary therapies.

Economic modelling

Two economic models were constructed to incorporate data from the reviews of effectiveness and cost effectiveness. The results are summarised in appendix C and the detailed reports of the economic models are 'Interventions to manage weight gain in pregnancy' and 'The cost-effectiveness of weight management interventions after childbirth'.

Fieldwork

Fieldwork was carried out to evaluate how relevant and useful NICE's recommendations are for practitioners and how feasible it would be to put them into practice. It was conducted with practitioners and commissioners who are involved in antenatal and postnatal care services, fertility services, leisure services, community groups, weight management services and children's centres. They included those working in the NHS, local authorities and organisations in the private, voluntary and community sectors.

The fieldwork comprised:

  • Three 1-day workshops carried out in London and Manchester with a total of 66 practitioners. They included commissioners, consultants in public health, food and nutrition advisers, midwives, obstetricians and public health specialists. They discussed all the draft recommendations including the role of leisure services, the voluntary sector and other non NHS organisations.

  • Three focus groups held in Doncaster, Harlow and Leicester with 26 practitioners. They included clinical and public health dietitians, consultant midwives, nurses, obesity coordinators and obstetric registrars. They discussed the recommendations in relation to pregnancy.

  • Four focus groups held in children's centres in Leeds, Liverpool, Newham and Sandwell with 21 practitioners. They included breastfeeding coordinators, children's centre managers, commissioning managers, community dietitians, community nutritionists and health visitors. They discussed the recommendations related to the period following childbirth.

  • Twenty-eight telephone interviews carried out with GPs, practice nurses and managers of children's centres and local authority leisure services. They discussed all the recommendations, particularly those most relevant to those professionals and services.

These four approaches were commissioned to ensure there was ample geographical coverage. The main issues arising are set out in appendix C under 'fieldwork findings'. The full fieldwork report is 'Weight management during pregnancy and after childbirth'.

How PHIAC formulated the recommendations

At its meetings in November 2009 and December 2009, PHIAC considered the evidence of effectiveness and cost effectiveness to determine:

  • whether there was sufficient evidence (in terms of quantity, quality and applicability) to form a judgment

  • whether, on balance, the evidence demonstrates that the intervention is effective, ineffective or equivocal

  • where there is an effect, the typical size of effect.

PHIAC developed draft recommendations through informal consensus, based on the following criteria.

  • Strength (type, quality, quantity and consistency) of the evidence.

  • The applicability of the evidence to the populations/settings referred to in the scope.

  • Effect size and potential impact on the target population's health.

  • Impact on inequalities in health between different groups of the population.

  • Equality and diversity legislation.

  • Ethical issues and social value judgements.

  • Cost effectiveness (for the NHS and other public sector organisations).

  • Balance of harms and benefits.

  • Ease of implementation and any anticipated changes in practice.

Where possible, recommendations were linked to evidence statements (see appendix C for details). Where a recommendation was inferred from the evidence, this was indicated by the reference 'IDE' (inference derived from the evidence).

The draft guidance, including the recommendations, was released for consultation in February 2010. At its meeting in April 2010, PHIAC amended the guidance in light of comments from stakeholders and experts and the fieldwork. The guidance was signed off by the NICE Guidance Executive in June 2010.