Appendix C: The evidence

This appendix lists evidence statements from two reviews provided by a public health collaborating centre (see appendix A) and links them to the relevant recommendations. (See appendix B for the key to quality assessments.) The evidence statements are presented here without references – these can be found in the full review (see appendix E for details). It also sets out a brief summary of findings from the economic analysis.

The two reviews of effectiveness are:

  • 'Systematic review of dietary and/or physical activity interventions for weight management in pregnancy'.

  • 'Systematic review of weight management interventions after childbirth'.

Evidence statement 1.3 indicates that the linked statement is numbered 3 in review 1. Evidence statement 2.3 indicates that the linked statement is numbered 3 in review 2.

The reviews, economic analysis and fieldwork report are available online. Where a recommendation is not directly taken from the evidence statements but is inferred from the evidence, this is indicated by IDE (inference derived from the evidence).

Recommendation 1: evidence statements 1.19, 1.20, 1.21, 1.22; IDE

Recommendation 2: evidence statements 1.1, 1.18, 1.20, 1.21, 1.26; IDE

Recommendation 3: evidence statements 1.3, 1.4, 1.7, 1.12, 1.14, 1.15, 1.16, 1.17, 1.19, 1.21, 1.22; IDE

Recommendation 4: evidence statements 2.1, 2.3, 2.6, 2.12, 2.13; IDE

Recommendation 5: evidence statements 1.1, 1.18, 2.1, 2.3, 2.6, 2.12, 2.13; IDE

Recommendation 6: IDE

Recommendation 7: evidence statements 1.16, 1.17, 1.19, 1.26; IDE

Evidence statements

Please note that the wording of some evidence statements has been altered slightly from those in the evidence reviews to make them more consistent with each other and NICE's standard house style.

Evidence statement 1.1

There is weak evidence from one Australian-based case series that obese women trying to become pregnant but experiencing infertility can achieve a statistically significant reduction in body mass index (BMI) through a programme that includes regular physical activity, advice about healthy eating and group support.

Evidence statement 1.3

There is evidence from two USA-based and one Canadian randomised controlled trial (RCT) (one [+] and two [−]) that interventions targeted at healthy weight or overweight pregnant women, encouraging a healthy diet and increased or regular physical activity, supported by weight monitoring, reduces the proportion of women exceeding Institute of Medicine (1990) guidelines for healthy weight gain in pregnancy.

Evidence statement 1.4

There is weak evidence from two studies (one [−] and one [+]), conducted in Denmark and Sweden among obese women that interventions promoting healthy eating and/or moderate physical activity leads to a reduction in weight retained postpartum when compared with controls.

Evidence statement 1.7

There were no adverse effects reported with moderate physical activity and/or dieting during pregnancy.

Evidence statement 1.12

There is evidence from one US-based observational study (++) that overweight women who consumed three or more servings of fruit and vegetables per day gained significantly less weight than those who consumed fewer servings during pregnancy.

Evidence statement 1.14

There is evidence from one US-based observational study (+) that not receiving advice regarding appropriate weight gain was associated with weight gain outside the recommended levels among women across the BMI spectrum.

Evidence statement 1.15

UK-based qualitative evidence (+) suggests that the development and attendance in dietary interventions for young women may be facilitated by taking into account women's age, social, educational and psychological needs as well as provision of incentives such as free food and access to a midwife.

Evidence statement 1.16

One UK-based qualitative study (+) retrospectively explored mothers' views on monitoring during their pregnancy/ies.

Women reported feeling that interactions with health professionals in relation to routine weighing were not enabling, and that they felt a lack of control. Women tended to be given limited explanation or feedback on weighing practices, although they accepted professional advice and intervention.

Routine monitoring of weight may not be acceptable to any women anxious about their weight without their consent, meaningful explanation and feedback.

Evidence statement 1.17

Health professionals reported (one [++]) that routine weighing of pregnant women was dependent on the location of the initial booking session. NHS premises tended to have resources for weighing whereas this was more ad-hoc in the community where scales may not be available and community midwives were not supplied with portable equipment. It was reported that even in NHS premises, equipment may not be suitable for weighing obese women.

Evidence statement 1.18

No UK-based qualitative evidence was identified on the views, perceptions and beliefs of health professionals, women actively planning a pregnancy and their partners and families about diet, physical activity and weight management prior to pregnancy. However, there is UK-based qualitative evidence to suggest that women's eating habits during pregnancy are related to pre-pregnancy dietary attitudes and behaviour. Weight and body shape concerns are affected by size prior to pregnancy (+). Women's dietary restraint may be continued or relaxed during pregnancy (+).

Evidence statement 1.19

Evidence from three UK-based qualitative studies (all [++]) suggests that weight management information and advice from professionals is not received or assimilated by many women during pregnancy. Available information is often vague, confusing, contradictory, and is not linked to weight management.

Overweight women may feel they are not receiving relevant, tailored information about appropriate diet and weight gain during pregnancy (+).

Evidence statement 1.20

There is evidence from UK-based qualitative research (one [+] and one [++]) that women may be unaware of the potential effects of obesity during pregnancy. However, they may avoid information about their health if they find it distressing and will only action it when they feel the time is right for the well-being of themselves, their unborn baby and their partners (+).

Evidence statement 1.21

There is evidence from UK-based qualitative research (++) that health professionals working in maternity units may feel they have insufficient time to discuss weight issues with women during pregnancy and consider that it is too late to give advice on weight management once a woman is pregnant. Health professionals themselves report that women's access to the information and advice on weight management is often ad-hoc.

Evidence statement 1.22

Evidence from two UK-based qualitative studies (one [++] and one [+]) suggests that even relatively active women reduce their physical activity during pregnancy (although they are more likely to continue to be active at some level). One study (++) found that pregnant women decreased their activity levels based on advice from health professionals, or more commonly, on information they had read in books and magazines. Family members, friends, and even health trainers tended to discourage physical activity. Women balanced their fears of injury to themselves or harm to the baby with aims toward weight management. Women also reported reduced motivation, physical limitations due to larger size and tiredness during pregnancy and a lack of facilities. Another study reported that pregnant women may feel self-conscious when carrying out physical activity (+).

Evidence statement 1.26

Qualitative evidence from two UK-based studies (one [++] and one [+]) suggest there are communication difficulties between overweight women and health professionals. One study of health professionals found that they are often embarrassed to discuss issues of weight with overweight women, and that the women themselves were also embarrassed (++). Such experiences may not be fixed, but may change over the course of a pregnancy.

One study (++) explored the views of health professionals, some of which found it difficult to raise this issue sensitively. They reported a lack of guidance on this issue, though were aware of the risks and benefit so raising the issue. They were concerned that some women may stop attending antenatal appointments if they felt victimised.

Evidence statement 2.1

There is limited evidence from one (+) US-based RCT that dietary intervention alone (aiming for 35% energy deficit) from 12 weeks postpartum, may help women across the BMI spectrum start to lose more weight after childbirth compared to usual care. However, the short length of this intervention (11 days) makes it difficult to draw conclusions on the effectiveness of the study. Four-day weighed food records suggested that calorie intake was not lower in the intervention compared to the control arm of the trial. The setting of this study (US) makes it somewhat relevant to the UK.

Evidence statement 2.3

Four out of five US-based RCTs addressing diet and physical activity postpartum found a significant reduction in total weight among women across the BMI spectrum in the intervention group compared to control (three [+] and one [−]). Only one (+) US-based RCT found that total weight was not significantly lower in the intervention group compared to control. Results did not appear to vary based on the start dates of intervention or the length of follow-up.

Evidence statement 2.6

In line with their results for weight loss, three RCTs from the US (two [+] and one [−]) found that an intervention focusing on diet and exercise resulted in decreased calorie intake and decreased consumption of foods such as sweet beverages, desserts and snacks. Of these studies, one also found a significant increase in energy expenditure between exercise groups (−) whereas another (+) found no significant difference in total energy expenditure between groups. One (+) did not report results for physical activity.

Evidence statement 2.12

The evidence suggests weight management interventions addressing diet and physical activity had little or no adverse effects on breastfeeding outcomes, including milk volume, infant intake and weight, time and frequency of feeding (two [+]). Milk protein was observed to decrease in one short US-based trial (+). Overweight women had higher milk energy outputs and leaner women saw a decrease in milk energy output.

Evidence statement 2.13

The one high quality (+) RCT which examined correlations between monitoring and weight loss found that there was a significant correlation between number of self-monitoring records returned and weight loss (r = 0.50, p < 0.005). However, homework completion or telephone contact with research staff was not significantly correlated with weight loss. Women enrolled in this trial had an above average BMI bordering on obese classification at start of the intervention. None of the included studies considered the effectiveness of monitoring alone.

Cost-effectiveness evidence

For weight management during pregnancy, a short-term model was applied. There was insufficient evidence of effect so the cost effectiveness estimation was subject to great uncertainty. For weight management after childbirth, the model used a study in which women's weight was measured at both 6 months and 15 years postpartum. This was compared with their pre- and post-pregnancy weight. Using a 15-year time horizon, the estimated cost per quality-adjusted life year (QALY) gained was £44,000. Using a lifetime horizon (the usual measure of cost effectiveness) it was £9000.

Fieldwork findings

Fieldwork aimed to test the relevance, usefulness and feasibility of putting the recommendations into practice. PHIAC considered the findings when developing the final recommendations. For details, go to the fieldwork section in appendix B and online.

Fieldwork participants in antenatal and postnatal care services, fertility services, leisure services, community groups, weight management services and children's centres were generally positive about the recommendations. They believed they could potentially help encourage weight management before, during and after pregnancy by raising awareness of the issue, especially among non-health professionals.

However, more focus was needed on the psychological and emotional issues linked to weight management. In addition, the importance of helping not just the women, but her whole family, to change their behaviour was emphasised.

Participants also said that the importance of breastfeeding – highlighting the health benefits and its role in weight management – needed to be stressed.

Practitioners felt that the recommendations were less relevant to some hard-to-reach groups such as women with a lower socioeconomic status, those from some minority ethnic groups and pregnant teenagers. In addition, there was mixed feedback regarding the feasibility of implementing them. Some reported that they reflected current practice. Others felt it would be difficult to carry them out.

The feasibility of carrying out the 6–8 week postnatal check on a consistent basis and the limited availability of dietitians in some areas were both cited as obstacles to implementation.

Participants emphasised that weight management is a sensitive issue. Many health professionals try to avoid broaching the subject and, when they do, it takes time. Training in communications skills was needed to deal with this type of issue, they said.

It was felt that the impact of the recommendations would vary across the country but that they would generally be more effective if actions and services were tailored to meet a woman's individual needs.

Participants pointed out that they would have cost and resource implications, due to the large number of women that they would apply to.

  • National Institute for Health and Care Excellence (NICE)