Abstract

Background: Complex interventions in obese pregnant women should be theoretically based, feasible and shown to demonstrate expected behavioural change prior to inception of large RCTs. The aim was to determine if (1) a complex intervention in obese pregnant women leads to expected changes in diet and PA behaviours, and (2) to refine the intervention protocol through process evaluation of intervention fidelity.

Methods: We undertook a pilot RCT of a complex intervention in obese pregnant women, comparing routine antenatal care with an intervention to reduce dietary GL and saturated fat intake and increase PA. Subjects included 183 obese pregnant women (mean BMI 36.3 kg/m²). Diet was assessed by repeated triple-pass 24-hour dietary recall and PA by accelerometry and questionnaire at 16⁺⁰–18⁺⁶ and at 27⁺⁰–28⁺⁶ weeks’ gestation in women in control and intervention arms. Attitudes to behaviour change and quality of life were assessed and a process evaluation undertaken. The full RCT protocol was undertaken to assess feasibility.

Results: Compared with women in the control arm, women in the intervention arm had a significant reduction in dietary GL (33 points, 95% CI −47 to −20 points), (p < 0.001) and saturated fat intake (−1.6% energy, 95% CI −2.8% to −0.3%) at 28 weeks’ gestation. Objectively measured PA did not change. Physical discomfort and sustained barriers to PA were common at 28 weeks’ gestation. Process evaluation identified barriers to recruitment, group attendance and compliance, leading to modification of intervention delivery.

Conclusions: This pilot trial of a complex intervention in obese pregnant women suggests greater potential for change in dietary intake than for change in PA, and through process evaluation illustrates the considerable advantage of performing an exploratory trial of a complex intervention in obese pregnant women before undertaking a large RCT.

Trial registration: Trial registration number ISRCTN89971375.

Background

Obesity is prevalent in women of reproductive age in both high- and low- to middle-income countries.⁸² Obese pregnant women have a heightened risk of adverse pregnancy outcomes,⁸² but at present there is no evidence-based intervention that can be introduced into clinical practice to improve pregnancy outcome in obese women. The majority of attempts to develop interventions have hitherto focused on limiting GWG in accordance with the US Institute of Medicine’s recommendations.⁸³ Recent meta-analyses of relevant studies in obese women show modest restriction of GWG without robust evidence for improved clinical outcome.^84,85 Limitations of the existing evidence include poor study design, small sample size, absence of a theoretical basis and, importantly, no a priori demonstration of the feasibility of the intervention in regard to changing the specific behaviours targeted. We have developed a theoretically based behavioural group intervention (diet and PA) for obese pregnant women with the primary aim of improving maternal glucose homeostasis. As maternal insulin resistance is integral to many complications of obese pregnancy, the dietary intervention focuses on lowering the dietary GI, previously shown to improve pregnancy outcome in women with GDM.^9,86 Recommendations were also made to lower saturated fat intake, as a diet high in saturated fats has been implicated in insulin resistance and GDM.⁸⁷ Increased PA can also improve metabolic control and reduce GDM risk in pregnant women.⁸⁸

Prior to embarking on a large RCT, and in accordance with UK Medical Research Council Guidance for development of a complex intervention,⁸⁹ we first explored the theoretical basis for an intervention in obese pregnant women,^2,3,85,90 leading to development of a novel intervention (phase 1). We now report on phase 2, an exploratory trial to determine whether or not this intervention achieved the changes in dietary and PA behaviours expected, and to undertake a process evaluation of every aspect of fidelity of the intervention and the protocol.

Participants

Potentially eligible participants attending clinics for general antenatal care were approached by research midwives in four UK study centres in urban settings providing a range of models of care. The contributing hospitals were (1) The Southern General Hospital and Princess Royal Maternity Hospital (Glasgow), (2) The Royal Victoria Infirmary (Newcastle), (3) Guy’s and St Thomas’ NHS Foundation Trust (London) and (4) King’s College Hospital Foundation Trust (London).

Methods

The protocol for the exploratory trial is shown in Figure 3. Verbal and printed information was provided to potential participants at a routine antenatal appointment in the first trimester of pregnancy and women were contacted > 24 hours later to ascertain willingness to participate. For those declining participation, consent to record basic demographic data and BMI was obtained. Those willing to participate were invited to return for their first study appointment in the early second trimester (> 15⁺⁰ to < 17⁺⁶ weeks’ gestation). This window of recruitment allowed adequate time for arrangement of the one-to-one session with the HT followed by the 8-week intervention programme prior to the oral glucose tolerance test (OGTT), carried out between 27⁺⁰ and 28⁺⁶ weeks’ gestation. Research midwives received a study-specific manual, attended at least one training session with the trial manager and continued feedback and training sessions for the study duration.

FIGURE 3

Pilot study protocol. EPDS, Edinburgh Postnatal Depression Scale; OGTT, oral glucose tolerance test; RPAQ, Recent Physical Activity Questionnaire.

Inclusion criteria: a BMI of ≥ 30 kg/m², singleton pregnancy and a gestational age of > 15⁺ and < 17⁺⁶ weeks.

Exclusion criteria: unable or unwilling to give written informed consent; gestation age of < 15⁺⁰ and > 17⁺⁶ weeks; pre-existing diabetes mellitus; pre-existing essential hypertension (treated); pre-existing renal disease; multiple pregnancy; systemic lupus erythematosus; antiphospholipid syndrome; sickle cell disease; thalassaemia; coeliac disease; currently prescribed metformin; thyroid disease; or current psychosis.

All data were entered onto a password-protected secure database (MedSciNet Ltd). Randomisation was performed online. The randomised treatment was allocated automatically, balanced by minimisation for maternal age, centre, ethnicity, parity and BMI. Data were analysed using Stata (version 11.2; StataCorp, College Station, TX, USA). All women randomised between 29 March 2010 and 13 May 2011 were included. Postcodes were matched to two national indices of deprivation: the Index of Multiple Deprivation⁹¹ for English addresses or the Scottish Index of Multiple Deprivation⁹² for addresses in Scotland.

Intervention delivery

The intervention was delivered by HTs. In the UK, HTs do not have prespecified health professional qualifications, but relevant experience [http://informationstrategy.dh.gov.uk/health-trainer-workforce (last accessed 10 March 2013), information now available at www.healthcareers.nhs.uk/explore-roles/public-health/health-trainer (last accessed 20 March 2017)]. All HTs received a comprehensive treatment manual, pre-study training (and within-study supervision) in behaviour modification and conducting group sessions (organised by Weight Concern; registered charity number 1059686). The sessions were held in a hospital setting in all but one centre, in which women attended a community children’s centre. At the initial one-to-one appointment women were provided with a participant handbook, reflecting the rationale and content of the HT sessions, a pedometer (Yamax SW200 Digi-Walker), a logbook for weekly SMART goals and related behaviours (steps, PA and diet) and a DVD of a specially devised pregnancy exercise regime. Potential benefits of attending group sessions were discussed. Each group session delivered a different element of the dietary and PA intervention. (Table 7). Goals from the previous week were reviewed and goals set for the following week. Discussion included barriers to behavioural change and ways these might be overcome.

TABLE 7

Summary of session content

The following information was obtained from all participants (at visits indicated in Figure 3).

Data handling and statistical analysis

Results

Figure 4 provides a flow chart of participants through the study.

FIGURE 4

The UPBEAT pilot study CONSORT diagram.

Participants

The mean first visit BMI was 36.3 kg/m². More than half the women were white and the remainder were from black (38%) and minority ethnic communities. More than half (56%) already had at least one child. More than half of those from centres in England and over 40% in Scotland came from regions in the highest quintile of social deprivation (Table 8).

TABLE 8

Description of subjects at baseline (16⁺⁰–18⁺⁶ weeks’ gestation) by randomised treatment

Diet and gestational weight gain

Table 9 shows the dietary intakes at baseline and at 28 weeks’ gestation. There were no differences between groups in energy intakes, GI, GL or other macronutrient at baseline. However, following the intervention, at 28 weeks’ gestation, total energy intake, dietary GL, GL (% energy), saturated fat (% energy) and total fat (% energy) were significantly lower, and fibre intake measured as non-starch polysaccharides was greater, in the intervention group than in the control arm. The proportion of energy derived from protein was higher in the intervention group, but absolute protein intake did not differ. There was a difference of 7 GI points between the intervention and control group, which achieved borderline statistical significance (p = 0.054).

TABLE 9

Dietary outcomes and GWG

There was a marginal difference in GWG of –0.9 kg between the intervention and control group at 28 weeks’ gestation (p = 0.065).

Physical activity

There were no differences between the intervention and the control arms in objectively measured PA variables at baseline or at 28 weeks’ gestation, after adjustment for baseline activity. Self-reported moderate to vigorous PA at 28 weeks’ gestation was increased in the intervention group (mean difference 34 minutes/day; 95% CI 9 to 59 minutes/day), but this was not supported by the objective data. Women in the intervention group self-reported walking for leisure for 14 minutes/day more than those in the control group at 28 weeks’ gestation (95% CI 5 to 23 minutes; p = 0.003). Agreement between the RPAQ questionnaire and accelerometry was very poor; for example, correlation between MVPA in the two formats at baseline was r = 0.275 (95% CI 0.107 to 0.428) and at 28 weeks’ gestation was r = −0.069 (95% CI –0.296 to 0.165) (Table 10).

TABLE 10

Physical activity as measured by accelerometer and RPAQ questionnaire

Attitudinal assessment of target behaviours

Benefits, barriers and confidence in making the target PA and dietary changes were unchanged in either the control and intervention groups from baseline to 28 weeks’ gestation (Table 11).

TABLE 11

Attitudes to target behaviours, quality of life and mental health assessment

Process evaluation

Context

This study coincided with the publication of new reports and guidance for obesity in pregnancy, with associated media coverage.^93,109 Most control group interviewees demonstrated awareness and reported taking steps to improve their diet or fitness (Box 1).

BOX 1

Process intervention findings (context: interventions and controls)

Reach

The mean age of those approached who were eligible for recruitment but declined to participate (n = 473) was 29.9 years and their mean BMI was 35.39 kg/m²; 59.7% were white, and 32.8% were black and 43.0% were in the lowest quintile for the Index of Deprivation, indicating the most severe deprivation. The characteristics of participants providing semistructured interviews (n = 21) are shown in Table 12. Their demographic profile was similar to that of study participants (see Table 7). Overall, 29 out of 183 (15.8%) women were lost to follow-up (see Figure 4).

TABLE 12

Structured interview sample characteristics compared with trial population

Dose

Of the 94 women randomised to the intervention, 82 (88%) attended at least one group session, and 60 (64%) attended four or more. A total of 42 women (45%) received material from all eight sessions, six by full attendance (6%) and the remainder when partly/wholly covered by subsequent telephone contact. The mean number of sessions attended or partly/wholly covered was 6.1 (SD 2.6).

Fidelity

The intervention package (eight HT group sessions) was provided with good consistency at each study site. Goals were set at all group sessions, of which 88% were considered SMART by HTs according to their diaries. The maximum group size was 5 (mean 2).

Acceptability

Women in both arms of the trial found the research processes acceptable and felt supported by the study midwives. Women in the intervention group were generally willing, in principle, to attend the eight HT sessions, and most women who attended valued the group approach, citing opportunities to raise questions and discuss each other’s experiences. Some were surprised at the extent of the intervention, having expected a less intensive, more advice-based approach. Consistency of attendance at the sessions varied for different reasons including work commitments, school pick-up times or feeling too unwell or tired. Occasionally initial involvement waned when groups proved smaller than expected, although the HT input by telephone or e-mail was considered valuable. Some women found the information contained in the handbook new, whereas for others it was too basic. The pedometers and step goals were generally well received. Setting and reflecting on weekly goals was motivational for most but could also invoke feelings of guilt, or a sense of being observed and judged. Women reported having watched the DVD, but few used it regularly.

When interviewees were asked whether or not they had made any changes as a result of the intervention, most reported some degree of change, especially in relation to dietary intake. Reported changes in PA were more limited, particularly because of pelvic pain or tiredness as pregnancy progressed. Women often reported aspirations to increase exercise postnatally (Box 2 and Table 13).

BOX 2

Evaluation of intervention

TABLE 13

Maternal and neonatal primary outcomes

Discussion

This study describes a pragmatic and rigorously evaluated pilot study of a complex intervention for diet and activity behaviour change in obese pregnant women. The intervention was associated with a significant change in dietary behaviour. Process evaluation showed overall acceptability of the protocol, but led to several refinements to improve acceptability and fidelity.

In any lifestyle intervention of diet and PA, it is important that the pilot study design includes methods to assess the potential of the intervention to change these behaviours in the expected direction of effect. Few assessments of dietary intake in similar investigations of overweight or obese women have been attempted.^110–112 We used a 24-hour recall method to assess dietary intake and, while this may lead to under-reporting of energy intakes, the reported values are not dissimilar to those of non-pregnant women in the general UK population.¹¹³ Both objectives of the dietary intervention, to bring about reductions in GL and the proportion of energy derived from SFAs, were achieved. This suggests that obese pregnant women are amenable to changing their diet in response to an intervention based on established theory, and that dietary advice, frequently delivered by health professionals, is likely to be successful in achieving dietary change in obese pregnant women, as previously implied.¹¹¹ The reduction in dietary GL achieved was similar (33% vs. 45%) to that reported in obese type 2 diabetic non-pregnant subjects, in whom improved glycaemic control was achieved.¹¹⁴ Recently, a similar intervention in 759 pregnant women showed a lower change in GL (13%), which was associated with a reduction in GWG in women who had previously delivered a LGA infant.¹¹⁵

The reduction in energy intake observed is consistent with other studies that have restricted the intake of fat from meat and dairy products and which has not been replaced by other sources of food energy.¹¹⁶ The reduced GL may also have contributed through effects on satiety.¹¹⁷ To our knowledge this is the first study demonstrating that expected changes in diet occur following delivery of an intervention to lower GL and saturated fat in obese pregnant women without GDM. Importantly, this occurred despite the focus being on reducing GL by lowering the intake of added sugars as well as advocating foods with a lower GI. Focusing on GI tends to modify the GL from starch, whereas the GI from sugar-sweetened beverages is less amenable to change. Consequently, dietary advice to decrease the intake of added sugar, particularly as sugar-sweetened beverages, is likely to have had an important impact on GL.

This study adds to the scant literature on the habitual diet of obese pregnant women. The macronutrient profile at randomisation was similar to that of women in the general population, with fibre (non-starch polysaccharides) intake below, and total sugars and saturated fat above, recommended UK guidelines.¹¹⁸ The overall energy intake and macronutrient profile accords with one previous report in obese pregnant women.¹¹¹ Because of the time required to rigorously assess diet using the 24-hour recall method, which, according to the process evaluation, is likely to have influenced recruitment and compliance, a short FFQ (5–10 minutes) was evaluated for use in the subsequent RCT.

The few studies that have attempted to measure changes in PA in intervention trials in pregnancy have generally relied on self-report, and results have been equivocal.^{111,119–122} Accelerometry, the standard method of objective assessment used previously in observational studies in pregnancy,¹²¹ has, to our knowledge, been employed in only one relevant RCT, the FitFor2 study,¹²³ a supervised exercise intervention in 121 overweight and obese women. Consistent with the Fitfor2 study, we found no effect of the intervention on PA using the ActiGraph accelerometer, concurring with the reported absence of change in barriers to PA. The failure of accelerometry to mirror the increase in self-reported walking in the intervention group could reflect insufficient intensity of this activity, but also reporting bias⁴⁹ that is common in the reporting of low-intensity activities, such as those frequently undertaken by pregnant women.⁴⁴ As reported elsewhere, compliance with accelerometry in pregnancy was an issue.^52,124

Nonetheless, 60% of obese pregnant women providing baseline accelerometry data met the current guidelines for PA in pregnancy (i.e. > 30 minutes of MVPA per day). A similar level of activity has been observed in pregnant women (all BMIs)⁵² and overweight and obese non-pregnant adults,¹²⁵ but not previously among obese pregnant women. Levels of PA were similar to those we found previously among overweight and obese women,⁴⁹ but substantially higher than those reported for non-pregnant women in the UK.¹²⁶ There is no consensus on change of MVPA over pregnancy.^{51,124,127,128} In this study of obese women, both groups reduced the level of objectively measured MVPA as pregnancy progressed.

This assessment has highlighted a critical need to evaluate PA behaviour objectively. We may otherwise have erroneously concluded in the following RCT that increased PA does not affect clinically relevant outcomes. Despite showing no increase in PA, we have not recommended that the RCT focuses on diet only,⁸⁴ but rather that women continue to be encouraged to adhere to PA recommended in clinical guidelines.

Although there were no changes in attitudinal outcomes, women were generally positive about the recommended dietary and PA behaviours despite perceived barriers to change. Attitudinal data relating to diet were comparable to those obtained in a population sample of pregnant women.³ The intervention did not achieve any reduction in perceived barriers but, despite this, important dietary changes were achieved, which may imply low levels of self-efficacy. However, barriers to increasing PA appeared too great to overcome, possibly reflecting increased physical discomfort with gestation, as indicated by the EQ-5D questionnaire.

The relationship between mental health, diet and PA in obese pregnancies warrants further investigation in the RCT in view of the high prevalence of depressive symptoms (EPDS score of > 12). Another report¹²⁹ has also found no effect on these symptoms of a complex behavioural intervention in obese women.

In terms of context, the process evaluation recruited women in urban hospitals serving regions with areas of high socioeconomic deprivation. Obesity rates are higher among women with lower socioeconomic status and fewer qualifications¹³⁰ and among particular ethnic groups, particularly black African and black Caribbean.¹³¹ It was important therefore to explore not only if recruitment was feasible, but also whether or not the intervention was acceptable to the women recruited. Prominent media coverage about obesity raised the possibility that women in the control group might proactively address diet and PA, and some interview data supported this, but the evaluation suggested that awareness through the media alone was not adequate to achieve sufficient behavioural change.

In relation to reach, just over one-third of eligible women agreed to participate. Similarly low recruitment rates are consistent with other intervention studies, particularly in populations with lower uptake of health care. In one previous relevant study of lifestyle advice in non-obese pregnant women, recruitment was slower than expected and low attendance at group exercise sessions and participant concern about burdensome data collection contributed to dropout.¹³² However, perceived advantages to participation such as extra clinical tests and continuity of care from research midwives supported study uptake and continuation. Given the continued rise in obesity in the adult population in England,¹³⁰ approximately one in five pregnant women would be eligible for inclusion. Recruitment of the numbers needed to be approached (4100) for the full trial is therefore unlikely to be affected by a shortage of eligible women.

Overall, the wide social and ethnic diversity among participants was similar in participants and those who declined, indicating that the intervention would be unlikely to increase health inequalities by attracting more educated and higher-income participants.¹³³ Importantly, although obese pregnant women, once recruited, were generally willing to attend group sessions, practicalities often interfered with regular attendance, thereby influencing dose.

However, the sessions did not appeal to all women. Some appreciated finding common issues with other group members, whereas others preferred one-to-one contact. Evidence for health improvement interventions in group settings is varied⁹³ and this study adds to the recognition that a ‘one size fits all’ approach may not be effective,¹³³ and that flexibility is key to retention. Fidelity was good with consistently high-level provision of SMART goals by HTs, which were viewed as a positive achievement, particularly since poor adherence to goal-setting has been associated with moderate attendance among pregnant women.¹³⁴ The high acceptability of the participant handbook and pedometer reinforced the theoretical approach,⁹⁴ and women also responded well to motivational techniques, but physical issues presented barriers to PA. The information provided was valued, including increasing awareness of safe PA in pregnancy, and seen to have important educational benefit. Several components of the intervention therefore appeared beneficial and were well received by women. The intervention is relatively intensive and presents costs for providers, and while a full assessment of cost and benefit was not conducted in this pilot, steps taken during the preclinical development phase (using HTs rather than clinicians to deliver the intervention, adopting local group-based approach) helped keep the overall costs of the intervention low, recognising that, if beneficial, it should also be affordable to health providers and to women. The rationale for this choice of HTs to deliver the intervention lay principally in the lower cost of employment compared with trained health professionals, and from our experience in working with Weight Concern, a charity which has pioneered self-help programmes and self-support groups for the treatment of obesity, and which was employed in this programme to train the HTs. All HTs were employed on the basis of having received some training in behaviour change techniques relevant to the delivery of the UPBEAT intervention. Another major advantage is that the expertise required is attainable within the participant materials and HT manuals. This was deliberate, so that it could be delivered by anyone who has received the appropriate training (as delivered as part of the RCT and pilot). Indeed, Weight Concern has previously used a peer-learning approach to good effect; importantly, this enables service providers to adapt the delivery (regarding who is delivering) according to their local population and skill set.

There was also suggestion from the process evaluation that the intervention may extend to peers and family, and some women aspired towards better fitness following birth. This study has reinforced earlier reports suggesting that rapport between study staff and participants, interviews requiring short time commitment and participants’ perception of the study as informative are all important recruitment and retention factors.¹³⁵ Formal evaluation of the reasons for the high refusal rate was not permissible because of ethical constraints, but the time commitment was frequently commented upon by the recruitment staff, as well as lack of appreciation of the health consequences of obesity in pregnancy.

In summary, this study has emphasised the value of a pilot trial to assess expected behaviour change. Although seldom attempted by others, we have also highlighted the importance of process evaluation in a complex intervention of diet and PA for pregnant women. The pilot trial demonstrated reductions in GL and in the proportion of energy derived from saturated fat are achievable in obese pregnant women without GDM. The process evaluation identified that dietary advice and education were well-received, and confirmed that PA change is more problematic to achieve, although it remains important to consistently measure and support PA using technologies acceptable to women. The process evaluation also helped explain issues arising in relation to uptake, dose, fidelity and retention which informed the feasibility of the full trial.

As a consequence of this study, several modifications to improve compliance and fidelity have now been implemented in the protocol for the main trial. As well as process evaluation, HT feedback highlighted potential barriers to fidelity of the intervention and informed protocol modifications for the RCT. Flexibility has been increased regarding the timing and delivery of the sessions, and goal-setting can be undertaken by telephone or e-mail. It is recommended that women should receive at least five out of eight sessions. The two extra visits required for objective assessment of PA and accurate evaluation of diet have been omitted in all but two sites (as planned) and dietary assessment reduced to a validated FFQ. The RPAQ includes domestic and childcare activities considered appropriate for pregnant women,¹³⁶ but following feedback has been replaced by the shorter and more relevant International Physical Activity Questionnaire (IPAQ).¹³⁷ Maintenance of dietary and PA behaviour change in the participant and her family is being formally evaluated at 6 months and at 3 years post partum. Although there was no significant influence of the intervention on objectively measured PA, and only a modest increase in self-reported MVPA, it was decided to continue to recommend PA, as this aligns with best practice as set out in clinical guidelines. To minimise loss to follow-up and attendance at these appointments, strategies that have been put in place include regular newsletters and sending greetings cards on special occasions such as the child’s birthday.

Conclusions

Assumptions should not be made that interventions in obese pregnant women necessarily change behaviour. We recommend that a pilot trial such as that described here, which has demonstrated evidence for expected change in behaviour, is a necessary prelude to any RCT of a complex intervention of diet and PA designed to improve pregnancy outcome in obese women. Without prior evidence for change in behaviour in the expected direction, pursuit of a large and costly trial would be futile. Similarly, we have demonstrated the value of early process evaluation, which can lead to important refinements in protocol to improve feasibility and compliance in the definitive trial.