Lifestyle interventions for overweight and obese pregnant women to improve pregnancy outcome: systematic review and meta-analysis

  • Eugene Oteng-Ntim1, 2, 3Email author,

    Affiliated with

    • Rajesh Varma1, 3,

      Affiliated with

      • Helen Croker4,

        Affiliated with

        • Lucilla Poston3 and

          Affiliated with

          • Pat Doyle2

            Affiliated with

            BMC Medicine201210:47

            DOI: 10.1186/1741-7015-10-47

            Received: 23 December 2011

            Accepted: 10 May 2012

            Published: 10 May 2012

            Abstract

            Background

            Overweight and obesity pose a big challenge to pregnancy as they are associated with adverse maternal and perinatal outcome. Evidence of lifestyle intervention resulting in improved pregnancy outcome is conflicting. Hence the objective of this study is to determine the efficacy of antenatal dietary, activity, behaviour or lifestyle interventions in overweight and obese pregnant women to improve maternal and perinatal outcomes.

            Methods

            A systematic review and meta-analyses of randomised and non-randomised clinical trials following prior registration (CRD420111122 http://​www.​crd.​york.​ac.​uk/​PROSPERO) and PRISMA guidelines was employed. A search of the Cochrane Library, EMBASE, MEDLINE, CINAHL, Maternity and Infant care and eight other databases for studies published prior to January 2012 was undertaken. Electronic literature searches, study selection, methodology and quality appraisal were performed independently by two authors. Methodological quality of the studies was assessed according to Cochrane risk of bias tool. All appropriate randomised and non-randomised clinical trials were included while exclusions consisted of interventions in pregnant women who were not overweight or obese, had pre-existing diabetes or polycystic ovarian syndrome, and systematic reviews. Maternal outcome measures, including maternal gestational weight gain, gestational diabetes and Caesarean section, were documented. Fetal outcomes, including large for gestational age and macrosomia (birth weight > 4 kg), were also documented.

            Results

            Thirteen randomised and six non-randomised clinical trials were identified and included in the meta-analysis. The evidence suggests antenatal dietary and lifestyle intervention in obese pregnant women reduces maternal pregnancy weight gain (10 randomised clinical trials; n = 1228; -2.21 kg (95% confidence interval -2.86 kg to -1.59 kg)) and a trend towards a reduction in the prevalence of gestational diabetes (six randomised clinical trials; n = 1,011; odds ratio 0.80 (95% confidence interval 0.58 to 1.10)). There were no clear differences reported for other outcomes such as Caesarean delivery, large for gestational age, birth weight or macrosomia. All available studies were assessed to be of low to medium quality.

            Conclusion

            Antenatal lifestyle intervention is associated with restricted gestational weight gain and a trend towards a reduced prevalence of gestational diabetes in the overweight and obese population. These findings need to be interpreted with caution as the available studies were of poor to medium quality.

            Background

            Both developed and developing countries are experiencing a rapid increase in the prevalence of obesity [13]. In the UK, 24% of women of reproductive age are now obese (body mass index (BMI) equal or greater than 30 kg/m2) and the prevalence appears to be increasing [4]. Studies in UK women show that the rates of obesity in pregnancy have almost doubled in the last two decades [5, 6]. Recent estimates suggest the prevalence of obesity in pregnancy in the UK is at least 20% with 5% having severe or morbid obesity [7, 8].

            Observational study data has linked obesity in pregnancy with adverse maternal and infant outcomes [710]. Obesity increases the risks of gestational diabetes [8, 1012], hypertensive disease (including pre-eclampsia) [8, 13, 14], thromboembolism [15, 16], infection [14, 17], Caesarean section [8, 18], congenital fetal anomalies [19], macrosomia [13], induction [20], stillbirth [12], shoulder dystocia [14] and preterm delivery [21]. Moreover, maternal obesity may impact on long-term outcomes such as the increasing weight of the child in infancy and the severity of obesity in future generations [10, 22, 23].

            As most of the adverse outcomes of obese pregnancies show strong associations with pre-pregnancy BMI, it is reasonable to assume that the ideal intervention would be to reduce obesity prior to pregnancy [24]. However, this is difficult to achieve because 50% of pregnancies in the UK are unplanned and a recent study concluded that only a small proportion of women planning pregnancy follow nutrition and lifestyle recommendations [25]. As such, an intervention pre-pregnancy may reach only a small proportion of the intended women.

            Alternatively, pregnancy itself may represent an ideal opportunity to target lifestyle change as women have increased motivation to maximise their own health and that of their unborn child [25]. However, evidence of benefit from published intervention studies appears limited and inconsistent [2644]. We therefore sought to determine the efficacy of combined dietary activity and behaviour support interventions in overweight and obese pregnant women by undertaking a systematic review and meta-analysis according to PRISMA (Transparent Reporting of Systematic Reviews and Meta-analyses) criteria for maternal clinical outcomes of weight gain, gestational diabetes and Caesarean section and infant outcomes, such as large for gestational age and macrosomia. Our aim was to generate data of the highest statistical power and sensitivity. Hence, in comparison with previous similar themed systematic reviews [4548], we chose to interrogate multiple databases (not restricted to English) and also separately meta-analyse randomised clinical trials (RCTs) and non-RCTs evaluating relevant clinical outcomes, including gestational diabetes and Caesarean section, which had not been attempted in prior meta-analyses.

            Methods

            Eligibility criteria

            The eligible studies included RCTs and non-RCTs that evaluated antenatal dietary and lifestyle interventions in obese and overweight pregnant women whose outcome measures included quantitative maternal and fetal health outcomes. Systematic reviews and trials of women with existing gestational diabetes, or trials of pre-conception or postpartum interventions, were not included. Inclusion of trials was not restricted by language, publication date or country. Systematic reviews and observational studies were excluded.

            Information sources

            Literature searches were performed using five mainstream electronic databases (Cochrane Library, MEDLINE, EMBASE, CINAHL, Maternity and Infant care), and eight other databases (PsyclINFO via OVID SP, PyscLNFO via OVID SP, Science Citation Index via Web of Science, Social Science Citation Index via Web of Science, Global Health, Popline, Medcarib, Nutrition database).

            Search strategy

            The following MeSH terms, words and combinations of words, were used in constructing the systematic search: overweight OR obesity; pregnancy OR pregnancy complications OR pregnancy outcome OR prenatal care, prenatal, antenatal, intervention, randomised controlled trial, life style, "early intervention (education)", health education, education, patient education handout, patient education, exercise, exercise therapy, health promotion, diet, carbohydrate-restricted, diet, fat-restricted, diet, reducing, diet therapy, weight loss. Full details of the search strategy are shown in Table 1. The searches were unlimited by time up to January 2012 and limited to human studies and clinical trials. The systematic search was undertaken in the mainstream databases and targeted searches were conducted in the other databases.
            Table 1

            Search strategy utilised for MEDLINE 1946 to January 2012

            Batch

            Search term (MESH)

            Combination

            Result

            1

            Pregnancy Complications/OR Pregnancy/OR Pregnancy Outcome/OR Pregnancy, High Risk/

             

            646,055

            2

            Prenatal Care/OR Pregnancy/OR Pregnancy Complications

             

            647,726

            3

            Antenatal.mp.

             

            18,393

            4

            Gestation intervention.mp.

             

            4

            5

             

            1 OR 2 OR 3 OR 4

            651,321

            6

            Overweight.mp. OR Obesity/OR Overweight/OR Body Weight/

             

            249,097

            7

            Obesity/OR Obesity, Morbid/or Obesity.mp.

             

            145,882

            8

            Body Weight/OR Obesity/OR Body Mass Index/or BMI.mp. OR Overweight/

             

            293,584

            9

             

            6 OR 7 OR 8

            328,089

            10

             

            5 AND 9

            21,583

            11

            Diet, Fat-Restricted/OR Diet/OR Diet, Protein-Restricted/OR Diet, Carbohydrate-Restricted/OR Diet.mp. OR Diet, Reducing/OR Diet Therapy/

             

            255,985

            12

            Life Style/

             

            36,837

            13

            Health Education/

             

            48,625

            14

            Patient Education as Topic/

             

            63,238

            15

            Exercise.mp. OR Exercise/OR Exercise, Therapy/

             

            192,937

            16

            Health Promotion/

             

            43,967

            17

            Weight Loss/

             

            19,434

            18

             

            11 OR 12 OR 13 OR 14 OR 15 OR 16 OR 17

            601,919

            19

             

            10 AND 18

            3,769

            20

             

            LIMIT 19 TO ((female or humans or pregnancy) and (clinical trial, all OR clinical trial, phase i OR clinical trial, phase ii OR clinical trial, phase iii OR clinical trial, phase iv OR clinical trial OR controlled clinical trial OR randomized controlled trial))

            154

            Study selection

            Electronic literature searches, study selection, methodology, appropriateness for inclusion and quality appraisal were performed independently and in duplicate by two authors (E-ON and RV). Disagreements between reviewers were resolved by consensus. Included studies were divided into two groups (RCTs and non-RCTs) and separately meta-analysed.

            Data collection process

            Two independent reviewers extracted the data. As a first step, each paper was screened using the title and the abstract. In the next round, studies were assessed for methodological quality and appropriateness for inclusion by two reviewers working independently from the full text of the manuscript. This was done without consideration of the results.

            Data items

            For each included trial, data was extracted on maternal gestational weight gain; gestational diabetes; Caesarean section; large for gestational age baby (> 4 kg); and birth weight. The included studies have been summarised in Tables 2 and 3.
            Table 2

            A summary of the studies that met the criteria of the systematic review on lifestyle interventions in overweight and obese pregnant women: randomised trials

            Author (year)

            Ethnic group/Country

            Participant/setting

            Sample size

            Intervention

            Outcome measure(s)

            Conclusion

            Polley et al. (2002) [32]

            31% black and 61% white/USA

            Recruited before 20 weeks of pregnancy (normal BMI > 19.5 to 24.9; overweight BMI ≥ 25 to < 30 kg/m2)/Hospital based

            120, including 49 overweight

            59 in control arm; 61 in intervention arm

            Exercise and nutrition information (oral and newsletter) Personalised graphs and behavioural counselling.

            Gestational weight gain; gestational diabetes; Caesarean section; birthweight

            No statistically significant reduction in gestational weight, prevalence of gestational diabetes, Caesarean section, or large for gestational age baby

            Hui et al. (2006) [33]

            Predominantly Caucasian/Canada

            Less than 26 weeks pregnant (community based and antenatal clinics). All BMI categories. Mean BMI of non-intervention arm = 25.7 (SD = 6.3) and for intervention arm = 23.4(SD = 3.9)

            45

            21 in non-intervention arm; 24 in intervention arm

            Physical exercise (group-sessions home-based exercise)

            Individualized nutrition plans

            Gestational weight gain

            No statistically significant reduction in gestational weight gain

            Wolff et al., 2008 [30]

            100% Caucasian/Denmark

            Obese (BMI ≥ 30 kg/m2) women enrolled at 15 weeks' gestation

            50 analysed

            23 in control arm; 27 in intervention arm

            Intensive intervention with 10 one-hour visits with a dietician at each antenatal visit, dietary guidance provided

            Gestational weight gain; gestational diabetes; Caesarean section; birthweight

            Statistically significant reduction in gestational weight gain, no statistically significant reduction in prevalence of gestational diabetes or Caesarean section, or birthweight

            Jeffries et al., 2009 [28]

            > 90% Caucasian/Australia

            Women at or below 14 weeks' gestation. All BMI categories included

            286

            138 in control arm; 148 in intervention arm

            Personalised weight measurement card (based on Institute of Medicine guidelines). Control had only single measurement at enrolment

            Gestational weight gain

            No statistically significant reduction in gestational weight gain.

            Ong et al., 2009 [42]

            Predominantly Caucasian/Australia

            Pregnant obese women recruited at 18 weeks' gestation

            12

            six in control arm; six in intervention arm

            Personalised 10 weeks of home-based supervised exercise (three sessions per week)

            Maternal aerobic fitness and gestational diabetes

            No statistically significant difference in aerobic fitness or gestational diabetes

            Barakat et al., 2011 [41]

            100% Caucasian/Spain

            All BMI categories

            160

            80 in control arm; 80 in intervention arm

            Three group-based sessions per week, light resistance and toning exercise from the second trimester

            Gestational weight gain and birthweight

            No statistically significant difference in gestational weight gain and birth weight. Exercise intervention might attenuate adverse consequences of maternal BMI on newborn birth size

            Asbee et al., 2009 [27]

            26% African American/USA

            Pregnant women recruited before 16 weeks' gestation. All BMI categories except those of BMI > 40 kg/m2

            100

            43 in control arm; 53 in intervention arm

            One session of dietetic counselling and activity

            Gestational weight gain; pregnancy outcome

            Statistically significant reduction in gestational weight gain. No effect on pregnancy outcome

            Thornton et al., 2009 [29]

            41% African American/USA

            Obese pregnant women (BMI ≥ 30 kg/m2) recruited between 12 and 28 weeks' gestation

            257 randomised.

            25 lost to follow up. 116 in control arm; 116 in intervention arm

            Nutritional regime for gestational diabetes

            Gestational weight gain; gestational diabetes; Caesarean section; pregnancy outcome

            Statistically significant reduction in gestational weight gain, no statistically significant reduction in prevalence of gestational diabetes, Caesarean section or birthweight

            Guelinckx et al., 2010 [26]

            100% Caucasian/Belgium

            Obese (BMI > 30 kg/m2) women enrolled at 15 weeks' gestation.

            195 randomised

            85 analysed

            65 in control arm; 65 in passive arm, 65 in intervention arm

            Three arms: group sessions with a dietician; written brochures; and standard care

            Dietary and physical activity guidance provided by dietician and in written brochures

            Nutritional habits; gestational weight gain; gestational diabetes; Caesarean section; birthweight

            Improved nutritional habits; no statistically significant reduction in gestational weight gain, prevalence of gestational diabetes, Caesarean section or birthweight.

            Phelan et al., 2011 [34]

            67% White/USA

            Pregnant women BMI between 19.8 and 40 kg/m2 recruited between 10 and 16 weeks' gestation

            401 randomised.

            201 in non-intervention arm; 200 in intervention arm

            Exercise and nutrition information (oral and newsletter) Personalised graphs and behavioural counselling

            Gestational weight gain; gestational diabetes; Caesarean section; pregnancy outcome

            Significant reduction in gestational weight gain; no statistically significant reduction in prevalence of gestational diabetes, Caesarean section or birthweight

            Quinlivan et al., 2011 [59]

            73% white, 19% Asian/Australia

            Pregnant women: overweight (BMI 25 to 29.9 kg/m2) and obese (BMI ≥ 30 kg/m2)

            132 randomised.

            65 in non-intervention arm; 67 in intervention arm

            Attended a study- specific antenatal clinic providing continuity of care, weighing on arrival, brief dietary intervention by food technologist and psychological assessment and intervention if indicated

            Gestational weight gain; gestational diabetes; birthweight

            Statistically significant reduction in gestational weight gain and prevalence of gestational weight gain. No statistically significant reduction in birthweight.

            Luoto et al., 2011 [43]

            Predominantly white/Finland

            Pregnant women at risk of gestational diabetes. All BMI ranges

            399 cluster randomised.

            219 in non-intervention arm; 180 in intervention arm

            Attended a study-specific individual antenatal lifestyle counselling clinic including group exercise

            Gestational diabetes; gestational weight gain; birthweight

            Statistically significant reduction in birthweight and macrosomia but no statistically significant difference in gestational diabetes

            Nascimento et al., 2011 [44]

            Predominantly white/Brazil

            Pregnant women of all BMI categories

            82 randomised.

            42 in non-intervention arm; 40 in intervention arm

            Attended a group-based exercise under supervision and received a home exercise counselling

            Gestational weight gain; raised blood pressure; perinatal outcome

            No statistically significant difference in gestational weight gain in terms of gestational weight gain, raised blood pressure or perinatal outcome

            BMI: body mass index; SD: standard deviation

            Table 3

            Summary of the studies that met the criteria of the systematic review on lifestyle interventions in overweight and obese pregnant women: non-randomised trials

            Author (year)

            Ethnic group/country

            Participants/setting

            Sample size

            Intervention

            Outcome measure(s)

            Conclusion

            Gray-Donald et al. (2000) [38]

            Native Americans/Canada

            Recruited before the 26th week of pregnancy, non-parallel recruitment of control and intervention arms.

            Mean BMI = 29.6 kg/m2 (SD = 6.45) in non-intervention arm and mean BMI = 30.8 kg/m2 (SD = 6.85) in intervention arm at baseline.

            219

            107 in non-intervention arm; 112 in intervention arm

            Dietary and weight counselling

            Exercise groups provided

            Gestational weight gain; gestational diabetes;

            Caesarean section;

            birthweight;

            postpartum weight retention

            No statistically significant difference in gestational weight gain, prevalence of gestational diabetes, Caesarean section or large for gestational age baby

            Olson et al. (2004) [51]

            96% white/USA

            Recruited before third trimester. Hospital and clinic setting

            BMI range: 19.8 to 29 kg/m2

            498

            381 in non-intervention arm; 117 in the intervention arm

            Used the Institute of Medicine recommended guidelines on weight gain; 'health book' used to record diet and exercise and contained healthy eating and exercise information

            Gestational weight gain; birthweight

            No statistically significant reduction in gestational weight gain or prevalence of large for gestational age baby

            Claesson et al. (2007) [36]

            Not stated. Predominantly Caucasian/Sweden

            Obese and registered at antenatal care clinic.

            BMI ≥ 30 kg/m2

            348

            193 in non-intervention arm; 155 in intervention arm

            Nutritional habits interview, weekly counselling and aqua aerobic sessions

            Gestational weight gain; Caesarean section.

            Statistically significant reduction in gestational weight gain; no difference in prevalence of Caesarean section

            Kinnunen et al. (2007) [37]

            Over 90% Caucasian/Finland

            First-time pregnant women who were obese (BMI ≥ 30 kg/m2)

            196

            95 in non-intervention arm; 101 in intervention arm

            Individual counselling at each antenatal visits. Dietary guidance and optional activity sessions.

            Gestational weight gain; diet change; birthweight

            No statistically significant reduction in gestational weight gain or prevalence of large for gestational age baby. Statistically significant reduction in dietary glycaemic load.

            Shirazian et al., 2010 [39]

            33% blacks; 67% Latino/USA

            Singleton obese (≥ 30 kg/m2) pregnant women recruited in the first trimester. Historical non-intervention group.

            54

            28 in non-parallel control arm; 28 in intervention arm)

            One-to-one counselling; six structured seminars on healthy living (healthy eating and walking)

            Gestational weight gain; gestational diabetes; Caesarean section

            Statistically significant reduction in gestational weight gain; no difference in prevalence of gestational diabetes

            Mottola et al., (2010) [35]

            Not stated/Canada

            Overweight (BMI ≥ 25 to 29.9 kg/m2) and obese (BMI ≥ 30 kg/m2) pregnant women recruited before 16 weeks' gestation; historical non-intervention group.

            65 matched non-parallel control of 260

            Individualised nutrition plan; exercise consisted of walking (three to four times per week, used pedometers)

            Gestational weight gain; Caesarean section; birthweight; peripartum weight retention

            Possible reduction in gestational weight gain; no difference in prevalence of Caesarean section or large for gestational age baby; minimal effect on peripartum weight retention

            BMI: body mass index; SD: standard deviation.

            Risk of bias in individual studies

            The quality of studies was assessed based on how the studies had minimised bias and error in their methods. We categorised the studies according to criteria based on PRISMA guidelines [49] and the Cochrane Library [50]. For example, high quality trials reported study aims; control comparison similar to the intervention group; relevant population demographics pre- and post-intervention; and data on each outcome. These study characteristics are tabulated in Tables 4 and 5. A final assessment categorised the studies as high, medium or low quality.
            Table 4

            Assessment of the quality of the included trials: non-randomised trials

            Author (year)

            Population representativeness

            Adequacy of sequence generation

            Masking/selection bias

            Incomplete outcome data

            Contamination

            Sample size

            Grade of quality

            Gray-Donald et al. (2000) [38]

            Yes: Registered from clinic

            No

            No

            No

            No: non-parallel control

            219

            Low

            Olson et al. (2004) [51]

            Yes

            No

            No

            No

            No: non-parallel control

            560

            Low

            Claesson et al. (2007) [36]

            Yes: Registered from clinic

            No

            No

            Yes

            No: selected from nearby city

            315

            Low

            Kinnunen et al. (2007) [37]

            Yes

            No

            No

            No

            Yes

            55

            Low

            Shirazian et al., (2010) [39]

            Yes

            No

            No

            Yes

            No: non-parallel control

            28

            Low

            Mottola et al., (2010) [35]

            Yes

            No

            No

            Yes

            No: non-parallel control

            65

            Low

            Table 5

            Assessment quality of included trials: randomised trials

            Author (year)

            Population representativeness

            Adequacy of sequence generation

            Masking/selection bias

            Intention to treat

            Incomplete outcome data

            Loss to follow up

            Sample size

            Grade of quality

            Polley et al. 2002 [32]

            Yes

            Yes:

            No

            Not reported

            No

            Yes

            120

            Low

            Hui et al. (2006) [33]

            Yes: from clinic

            Exact method not described

            No

            Not reported

            No

            Yes

            52

            Low

            Wolff et al., 2008 [30]

            Yes

            Yes: computer generated

            No

            Not reported

            Yes

            Yes

            50

            Low

            Jeffries et al., 2009 [28]

            Yes

            Yes: Opaque envelope

            Yes

            Not reported

            Yes

            Yes

            286

            Low

            Ong et al., 2009 [42]

            Yes

            Exact method not described

            No

            Not reported

            No

            No

            12

            Low

            Barakat et al., 2011 [41]

            Yes

            Yes

            Yes

            Yes

            Yes

            Yes

            160

            Medium

            Asbee et al. 2009 [27]

            Yes

            Yes

            No

            Not reported

            Yes

            No

            100

            Low

            Thornton et al., 2009 [29]

            Yes

            Yes

            Yes

            Not reported

            Yes

            Yes

            257

            Medium

            Guelinckx et al., 2010 [26]

            Not reported

            Randomised but not reported how

            Not reported

            Not reported

            Yes

            Not reported

            99

            Low

            Phelan et al., 2011 [34]

            Yes

            Yes: Opaque envelope

            Yes

            Yes

            Yes

            Yes

            401

            Medium,

            Quinlivan et al., 2011 [59]

            Yes

            Yes: Opaque envelope

            Yes

            Yes

            Yes

            Yes

            124

            Medium

            Luoto et al., 2011 [43]

            Yes

            Yes

            Yes

            Yes

            Yes

            Yes

            399

            Medium

            Nascimento et al., 2011 [44]

            Yes

            Yes: Opaque envelope

            Yes

            Yes

            Yes

            Yes

            82

            Low

            Summary and analysis of studies that meet the criteria

            This is shown in Figure 1 and in a tabulated format contained within Table 2 and 3.
            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig1_HTML.jpg
            Figure 1

            Flow diagram of study selection.

            Summary measures and data synthesis

            The main measure of effect of the meta-analysis was the odds ratio or standardised mean difference. The data syntheses were conducted according to the Cochrane methodology [50]. First, we used statistical meta-analysis techniques to assess the efficacy of the interventions of controlled trials. Chi-square statistics tests were used to test for heterogeneity (Q statistics) between controlled trials. When there was no significant heterogeneity, we combined effect sizes in a fixed effect statistical meta-analysis using Review Manager (RevMan; Version 5.0, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2008). The meta-analyses were performed by calculating the odds ratios (for proportion data) or standardised mean differences (for scale data) using a fixed effects model. Quantitative analysis was performed on an intention-to-treat basis focused on data derived from the period of follow-up. There was heterogeneity between studies because of the smaller sample size of some of the studies (poor quality), variation of the study population and the intensity and duration of the interventional strategies being evaluated. A random effects model was used to adjust for heterogeneity.

            Results

            Study characteristics

            The review process is outlined in Figure 1 and the selected papers summarised in Tables 2 and 3.

            Fifteen trials met the inclusion criteria: 13 RCTs [2634] and six non-RCTs [35, 36, 38, 39, 51, 52]. All 19 trials were performed in developed countries: five in the USA, three in Canada, three in Australia, two in Finland and one in Denmark, Netherlands, Sweden, Spain, Brazil and Belgium (Tables 2 and 3). Five RCTs were judged to be of medium quality [27, 29, 34]. The rest were deemed low quality (Tables 4 and 5).

            The pooled RCTs included a total of 1,228 participants and the pooled non-RCTs included 1,534 participants. Participants were predominantly white except in the studies by Asbee et al. [27], Gray-Donald et al. [38] and Hui et al. [33]. In the Asbee et al. study, the majority were described as being of Hispanic ethnicity [27].

            For all included RCTs, the control group received no intervention or standard care. In the non-RCTs, most used non-parallel controls [35, 38, 39, 51] or controls from another centre [36]. The outcomes investigated in the trials were gestational weight gain, gestational diabetes, Caesarean section delivery, large for gestational age baby and birth weight.

            Effects of the intervention on outcomes

            Of the 19 controlled trials, 16 measured gestational weight gain (10 randomised, 6 non-randomised); 8 recorded gestational diabetes (6 randomised, 2 non-randomised); 10 recorded Caesarean delivery (6 randomised, 4 non-randomised); 10 measured large for gestational age (6 randomised, 4 non-randomised); and 7 measured birth weight (7 randomised). Meta-analyses for the different outcomes are shown in Tables 6 and 7, and Figures 2, 3, 4, 5, 6, 7, 8, 9 and 10.
            Table 6

            Effect estimates for randomised trials of lifestyle advice versus standard care

            Outcome or subgroup

            Studies

            Participants

            Statistical method

            Effect estimate

            Large for gestational age

            6

            1,008

            Odds ratio (Fixed, 95% CI)

            0.91 (0.62, 1.32)

            Caesarean delivery

            6

            663

            Odds ratio (Fixed, 95% CI)

            0.96 (0.68, 1.36)

            Gestational diabetes

            6

            1,017

            Odds ratio (M-H, Fixed, 95% CI)

            0.80 (0.58, 1.10)a

            Gestational weight gain (kg)

            10

            1,228

            Mean difference (Fixed, 95% CI)

            -2.21 (-2.86, -1.57)a

            Birth weight (g)

            7

            1,133

            Mean difference (Fixed, 95% CI)

            -56.64 (-120.15, 6.88)

            aStatistically significant pooled estimates. CI: confidence interval

            Table 7

            Effect estimates for non-randomised trials of lifestyle advice versus standard care

            Outcome or subgroup

            Studies

            Participants

            Statistical method

            Effect estimate

            Large for gestational age

            4

            1,199

            Odds ratio (Fixed, 95% CI)

            0.85 (0.63, 1.16)

            Caesarean delivery

            4

            1,246

            Odds ratio (Fixed, 95% CI)

            1.13 (0.78, 1.64)

            Gestational diabetes

            2

            233

            Odds ratio (Fixed, 95% CI)

            1.51 (0.72, 3.16)

            Gestational weight gain (kg)

            6

            1,534

            Mean difference (Fixed, 95% CI)

            -0.42 (-1.03, 0.19)

            CI: confidence interval

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig2_HTML.jpg
            Figure 2

            Forest plot of randomised trials investigating the effect of lifestyle advice versus standard care on gestational weight gain (kg).

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig3_HTML.jpg
            Figure 3

            Forest plot of randomised trials investigating the effect of lifestyle advice versus standard care on risk of gestational diabetes.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig4_HTML.jpg
            Figure 4

            Forest plot of randomised trials investigating the effect of lifestyle advice versus standard care on risk of Caesarean delivery.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig5_HTML.jpg
            Figure 5

            Forest plot of randomised trials investigating the effect of lifestyle advice versus standard care on risk of large for gestational age baby.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig6_HTML.jpg
            Figure 6

            Forest plot of randomised trials investigating the effect of lifestyle advice versus standard care on birthweight.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig7_HTML.jpg
            Figure 7

            Forest plot of non-randomised trials investigating the effect of lifestyle advice versus standard care on risk of large for gestational age baby.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig8_HTML.jpg
            Figure 8

            Forest plot of non-randomised trials investigating the effect of lifestyle advice versus standard care on risk of Caesarean section.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig9_HTML.jpg
            Figure 9

            Forest plot of non-randomised trials investigating the effect of lifestyle advice versus standard care on risk of gestational diabetes.

            http://static-content.springer.com/image/art%3A10.1186%2F1741-7015-10-47/MediaObjects/12916_2011_526_Fig10_HTML.jpg
            Figure 10

            Forest plot of non-randomised trials investigating the effect of lifestyle advice versus standard care on gestational weight gain (kg).

            Meta-analysis of RCTs showed that combined antenatal lifestyle, dietary and activity intervention restricts gestational weight gain (Table 6 and Figure 2) and there was a trend towards reduction in the prevalence of gestational diabetes in overweight and obese women (Table 6 and Figure 3). However, meta-analysis of non-RCTs only showed weak evidence that lifestyle intervention reduces gestational weight gain (Table 7 and Figure 7) and there was no evidence for a reduction in prevalence of gestational diabetes (Table 7 and Figure 8). There was no robust evidence that lifestyle intervention is associated with a lower prevalence of Caesarean delivery or macrosomia or any alteration in birth weight (Tables 6 and 7, Figures 4,5, 6, 8, 9 and 10).

            Intervention characteristics

            The nature of the interventions varied widely between studies and some of the key features of the interventions are outlined in Tables 2 and 3. In summary, for the six non-RCTs, three of the interventions comprised individual and group or seminar components [36, 38, 39, 53], two were individual [35, 52] and one was unclear [51]. Of the 13 RCTs, one comprised individual and group components [33], eight were individual [2730, 32, 34] and three were group-based [26]. Where there were individual and group components, the latter were usually physical activity sessions. All of the non-RCTs included dietary and physical activity guidance, as did the majority of the randomised studies. Exceptions were two studies which included only nutritional guidance [29, 30] and one which included guidelines about weight gain and weight monitoring only [28]. The majority of studies included dietary or physical activity guidance, with one of the non-RCTs [35] and three of the RCTs [29, 3234] specifying that guidance was personalised.

            Discussion

            Summary of main findings

            Antenatal lifestyle, dietary and activity advice for overweight and obese pregnant women restricts maternal weight gain during pregnancy and lowers the prevalence of gestational diabetes in women who are overweight or obese. However, the quality of the study designs was generally poor. The reduction in gestational weight gain was observed to be statistically significant in the meta-analysis of randomised trials (10 RCTs; n = 1,228; -2.21 kg (95% CI, -2.86 to -1.57 kg)) but non-significant in the meta-analysis of non-randomised trials (six non-RCTs; n = 1,534). No effects of antenatal lifestyle interventions were identified in obese and overweight pregnant women in relation to Caesarean delivery, large for gestational age, birth weight and macrosomia (> 4 kg).

            Interpretation

            There is evidence to suggest antenatal lifestyle interventions may restrict gestational weight gain and a trend towards a reduced prevalence of gestational diabetes, but there was no statistical effect on other important clinical outcomes, possibly due to inadequate power of the combined sample size. The effect on restricted weight gain and gestational diabetes was not consistent across all the trial populations and therefore cannot be generalised. There was also wide variation in the types of interventions evaluated in the studies. The majority were individual-based and most provided generic guidance comprising mainly dietary and physical activity information, with few tailoring guidelines. There was considerable heterogeneity in intervention design and no obvious patterns between intervention type and study outcomes. For the gestational weight gain and gestational diabetes outcomes, both the successful and non-successful studies included those which were personalised, combined physical activity and dietary guidance and were individual-based. Moreover, degrees of weight gain restriction achieved were modest overall. It is even harder to make conclusions regarding the specific behaviour change strategies included (for example, monitoring and goal setting) or theoretical basis of interventions since these were typically poorly reported.

            Identifying specific components of successful interventions aids understanding of how interventions are having an effect and clear reporting of intervention design allows for easier replication [54]. Previous reviews have attempted to make conclusions regarding specific effective components of interventions. Suggestions that weight monitoring and setting weight goals could be useful [46] and also monitoring along with education counselling and physical activity sessions [51, 55] have been made. Another review suggested that interventions should be based on the Theory of Planned Behaviour, but the rationale for using this model over others in this population was unclear [56]. None of these reviews examined intervention components systematically. A more recent review by Gardner et al. assessed interventions targeting gestational weight gain from a psychological perspective and specifically examined intervention content and delivery methods [57]. This review comprised 10 controlled trials, all included in the current review; only two of the studies reported basing interventions on theory and the studies used, on average, five behaviour change strategies (self-monitoring, feedback provision and setting behavioural goals were the most common), but no conclusions could be drawn as to their contribution to study outcomes. Broadly consistent with this were the four studies in the current review which were not included in the review by Gardner et al. [57]. Their review questioned the evidence supporting the benefits of weight monitoring, but tentatively suggested that information provision had been underused and that it might be of benefit to have a narrower focus of intervention targets [57].

            Comparison with other systematic reviews and strengths

            Our study adds to a growing body of evidence that aims to evaluate lifestyle intervention as a means to minimise the adverse outcome associated with obesity in pregnancy. In comparison to other published reviews [45, 46, 56], we have adopted an original approach by broadening the literature source (multiple data sources, no language restriction), focusing on relevant clinical outcomes (such as Caesarean section, gestational diabetes, macrosomia), and improving our sensitivity by meta-analysing both RCTs and non-RCTs. Furthermore, to minimise bias, the review methodology was registered a priori (Prospero number CRD420111122 http://​www.​crd.​york.​ac.​uk/​PROSPERO). We therefore believe our review provides a comprehensive and reliable analysis of the current evidence and for the first time highlights that lifestyle intervention in pregnancy may reduce the prevalence of gestational diabetes.

            Limitations of this systematic review

            The evidence summarised in this work comes from available studies of which most are of low quality, with only four studies fulfilling a medium quality score. Hence, the evidence base is weak and calls for more robust studies. Our trial population is relatively small, the intensity and duration of the interventions of trials varied and trials were predominantly USA in origin; a phenomenon common to many public health reviews, especially on obesity. Although our focus was on antenatal lifestyle intervention for obese and overweight pregnant women, our search yielded some studies that contained a mixed group of obese and normal weight women and we excluded all the non-obese participants from our analysis. Still, this may lead to inconsistencies in measuring the effect of the intervention as well as under- or overestimating the treatment effect. Furthermore, even though our search was systematic and rigorous, we could have missed eligible studies inadvertently.

            Conclusions

            This review reveals that lifestyle interventions for obese and overweight women during pregnancy restrict gestational weight gain and a trend was evident towards reducing the prevalence of gestational diabetes. However, the quality of the published studies is mainly poor. This then highlights a paradox. At a time when solutions to address adverse outcome associated with maternal overweight and obesity are identified as a public health priority, we find that most of the research evidence lacks robustness to inform future evidence-based lifestyle interventions for obese pregnant women. There is thus a research gap regarding the effectiveness of lifestyle intervention in pregnancy. It is unlikely that further meta-analysis will help to refine the quality of evidence because studies demonstrated significant heterogeneity in relation to demography, outcome measurement, follow-up and degree of intervention. Hence, we conclude that there is the need for a well-designed large-scale prospective trial which examines combined antenatal lifestyle interventions in obese pregnant women that is suitably powered and incorporates robust methodology in accordance with standards set by Medical Research Council's framework for evaluating complex interventions [58]. There are two such studies which are currently ongoing called LIMIT (ACTRN 12607000161426) and UPBEAT (ISRCTN89971375). Both of these studies are appropriately powered to show convincingly whether lifestyle intervention is most likely to improve pregnancy outcome or not.

            Declarations

            Acknowledgements

            We acknowledge Lisa Xue, Royal College of Obstetricians and Gynaecologists Librarian, for her help in acquiring most of the manuscripts in time. We also acknowledge Guy's and St Thomas' charity for supporting E-ON. This manuscript presents independent research commissioned by the National Institute for Health Research (NIHR, UK) under the programme grants for Applied Research programme RP-0407-10452. The views expressed in this manuscript are those of the authors and not necessarily those of the National Health Service, the NIHR or the Department of Health.

            Authors’ Affiliations

            (1)
            Department of Women’s Health, Guy’s and St Thomas’ NHS Foundation Trust (King’s Health Partners), St Thomas’ Hospital
            (2)
            London School of Hygiene and Tropical Medicine
            (3)
            School of Medicine, King’s College London
            (4)
            Department of Epidemiology and Public Health, University College London

            References

            1. Haslam DW, James WP: Obesity. Lancet 2005, 366:1197–1209.PubMedView Article
            2. Low S, Chin MC, Deurenberg-Yap M: Review on epidemic of obesity. Ann Acad Med Singapore 2009, 38:57–59.PubMed
            3. Finucane MM, Stevens GA, Cowan MJ, Danaei G, Lin JK, Paciorek CJ, Singh GM, Gutierrez HR, Lu Y, Bahalim AN, Farzadfar F, Riley LM, Ezzati M, Global Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group (Body Mass Index): National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9.1 million participants. Lancet 2011, 377:557–567.PubMedView Article
            4. Aylott J, Brown I, Copeland R, Johnson D: Tackling obesity: the foresight report and implication for local government. [http://​www.​idea.​gov.​uk/​idk/​aio/​8268011] 2008.
            5. Kanagalingam MG, Forouhi NG, Greer IA, Sattar N: Changes in booking body mass index over a decade: retrospective analysis from a Glasgow Maternity Hospital. BJOG 2005, 112:1431–1433.PubMedView Article
            6. Heslehurst N, Ells LJ, Simpson H, Batterham A, Wilkinson J, Summerbell CD: Trends in maternal obesity incidence rates, demographic predictors, and health inequalities in 36,821 women over a 15-year period. BJOG 2007, 114:187–194.PubMedView Article
            7. Heslehurst N, Rankin J, Wilkinson JR, Summerbell CD: A nationally representative study of maternal obesity in England, UK: trends in incidence and demographic inequalities in 619 323 births, 1989–2007. Int J Obes (Lond) 2010, 34:420–428.View Article
            8. Centre for Maternal and Child Enquiries: Maternal obesity in the United Kingdom: findings from a national project. [http://​www.​oaa-anaes.​ac.​uk/​assets/​_​managed/​editor/​File/​CMACE/​CMACE_​Obesity_​Report_​2010_​Final%20​for%20​printing.​pdf] 2010.
            9. Sebire NJ, Jolly M, Harris JP, Wadsworth J, Joffe M, Beard RW, Regan L, Robinson S: Maternal obesity and pregnancy outcome: a study of 287,213 pregnancies in London. Int J Obes Relat Metab Disord 2001, 25:1175–1182.PubMedView Article
            10. Poston L: Developmental programming and diabetes - the human experience and insight from animal models. Best Pract Res Clin Endocrinol Metab 2010, 24:541–552.PubMedView Article
            11. Yogev Y, Visser GH: Obesity, gestational diabetes and pregnancy outcome. Semin Fetal Neonatal Med 2009, 14:77–84.PubMedView Article
            12. Torloni MR, Betran AP, Horta BL, Nakamura MU, Atallah AN, Moron AF, Valente O: Prepregnancy BMI and the risk of gestational diabetes: a systematic review of the literature with meta-analysis. Obes Rev 2009, 10:194–203.PubMedView Article
            13. Chu SY, Callaghan WM, Kim SY, Schmid CH, Lau J, England LJ, Dietz PM: Maternal obesity and risk of gestational diabetes mellitus. Diabetes Care 2007, 30:2070–2076.PubMedView Article
            14. O'Brien TE, Ray JG, Chan WS: Maternal body mass index and the risk of preeclampsia: a systematic overview. Epidemiology 2003, 14:368–374.PubMedView Article
            15. Larsen TB, Sorensen HT, Gislum M, Johnsen SP: Maternal smoking, obesity, and risk of venous thromboembolism during pregnancy and the puerperium: a population-based nested case-control study. Thromb Res 2007, 120:505–509.PubMedView Article
            16. Knight M: Antenatal pulmonary embolism: risk factors, management and outcomes. BJOG 2008, 115:453–461.PubMedView Article
            17. Usha Kiran TS, Hemmadi S, Bethel J, Evans J: Outcome of pregnancy in a woman with an increased body mass index. BJOG 2005, 112:768–772.PubMedView Article
            18. Poobalan AS, Aucott LS, Precious E, Crombie IK, Smith WC: Weight loss interventions in young people (18 to 25 year olds): a systematic review. Obes Rev 2010, 11:580–592.PubMedView Article
            19. Stothard KJ, Tennant PW, Bell R, Rankin J: Maternal overweight and obesity and the risk of congenital anomalies: a systematic review and meta-analysis. JAMA 2009, 301:636–650.PubMedView Article
            20. Zhang J, Bricker L, Wray S, Quenby S: Poor uterine contractility in obese women. BJOG 2007, 114:343–348.PubMedView Article
            21. Smith GC, Shah I, Pell JP, Crossley JA, Dobbie R: Maternal obesity in early pregnancy and risk of spontaneous and elective preterm deliveries: a retrospective cohort study. Am J Public Health 2007, 97:157–162.PubMedView Article
            22. Poston L, Harthoorn LF, van der Beek EM: Obesity in pregnancy: implications for the mother and lifelong health of the child. A consensus statement. Pediatr Res 2011, 69:175–180.PubMedView Article
            23. Ludwig DS, Currie J: The association between pregnancy weight gain and birthweight: a within-family comparison. Lancet 2010, 376:984–990.PubMedView Article
            24. Nohr EA, Vaeth M, Baker JL, Sorensen T, Olsen J, Rasmussen KM: Combined associations of prepregnancy body mass index and gestational weight gain with the outcome of pregnancy. Am J Clin Nutr 2008, 87:1750–1759.PubMed
            25. Inskip HM, Crozier SR, Godfrey KM, Borland SE, Cooper C, Robinson SM: Women's compliance with nutrition and lifestyle recommendations before pregnancy: general population cohort study. BMJ 2009, 338:b481.PubMedView Article
            26. Guelinckx I, Devlieger R, Mullie P, Vansant G: Effect of lifestyle intervention on dietary habits, physical activity, and gestational weight gain in obese pregnant women: a randomized controlled trial. Am J Clin Nutr 2010, 91:373–380.PubMedView Article
            27. Asbee SM, Jenkins TR, Butler JR, White J, Elliot M, Rutledge A: Preventing excessive weight gain during pregnancy through dietary and lifestyle counseling: a randomized controlled trial. Obstet Gynecol 2009, 113:305–312.PubMed
            28. Jeffries K, Shub A, Walker SP, Hiscock R, Permezel M: Reducing excessive weight gain in pregnancy: a randomised controlled trial. Med J Aust 2009, 191:429–433.PubMed
            29. Thornton YS, Smarkola C, Kopacz SM, Ishoof SB: Perinatal outcomes in nutritionally monitored obese pregnant women: a randomized clinical trial. J Natl Med Assoc 2009, 101:569–577.PubMed
            30. Wolff S, Legarth J, Vangsgaard K, Toubro S, Astrup A: A randomized trial of the effects of dietary counseling on gestational weight gain and glucose metabolism in obese pregnant women. Int J Obes (Lond) 2008, 32:495–501.View Article
            31. Yeo S: A randomized comparative trial of the efficacy and safety of exercise during pregnancy: design and methods. Contemp Clin Trials 2006, 27:531–540.PubMedView Article
            32. Polley BA, Wing RR, Sims CJ: Randomized controlled trial to prevent excessive weight gain in pregnant women. Int J Obes Relat Metab Disord 2002, 26:1494–1502.PubMedView Article
            33. Hui AL, Ludwig SM, Gardiner P, Sevenhuysen G, Murray R, Morris M, Shen GX: Community based excercise and dietary intervention during pregnancy: a pilot study. Canadian Journal of Diabetes 2006, 30:169–175.
            34. Phelan S, Phipps MG, Abrams B, Darroch F, Schaffner A, Wing RR: Randomized trial of a behavioral intervention to prevent excessive gestational weight gain: the Fit for Delivery Study. Am J Clin Nutr 2011, 93:772–779.PubMedView Article
            35. Mottola MF, Giroux I, Gratton R, Hammond JA, Hanley A, Harris S, McManus R, Davenport MH, Sopper MM: Nutrition and exercise prevent excess weight gain in overweight pregnant women. Med Sci Sports Exerc 2010, 42:265–272.PubMed
            36. Claesson IM, Sydsjo G, Brynhildsen J, Cedergren M, Jeppsson A, Nystrom F, Sydsjö A, Josefsson A: Weight gain restriction for obese pregnant women: a case-control intervention study. BJOG 2008, 115:44–50.PubMed
            37. Kinnunen TI, Aittasalo M, Koponen P, Ojala K, Mansikkamaki K, Weiderpass E, Fogelholm M, Luoto R: Feasibility of a controlled trial aiming to prevent excessive pregnancy-related weight gain in primary health care. BMC Pregnancy Childbirth 2008, 8:37.PubMedView Article
            38. Gray-Donald K, Robinson E, Collier A, David K, Renaud L, Rodrigues S: Intervening to reduce weight gain in pregnancy and gestational diabetes mellitus in Cree communities: an evaluation. CMAJ 2000, 163:1247–1251.PubMed
            39. Shirazian T, Monteith S, Friedman F, Rebarber A: Lifestyle modification program decreases pregnancy weight gain in obese women. Am J Perinatol 2010, 27:411–414.PubMedView Article
            40. HAPO Study Cooperative Research Group: Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study: associations with neonatal anthropometrics. Diabetes 2009, 58:453–459.View Article
            41. Barakat R, Cordero Y, Coteron J, Luaces M, Montejo R: Exercise during pregnancy improves maternal glucose screen at 24–28 weeks: a randomised controlled trial. Br J Sports Med 2011, in press.
            42. Ong MJ, Guelfi KJ, Hunter T, Wallman KE, Fournier PA, Newnham JP: Supervised home-based exercise may attenuate the decline of glucose tolerance in obese pregnant women. Diabetes Metab 2009, 35:418–421.PubMedView Article
            43. Luoto R, Kinnunen TI, Aittasalo M, Kolu P, Raitanen J, Ojala K, Mansikkamäki K, Lamberg S, Vasankari T, Komulainen T, Tulokas S: Primary prevention of gestational diabetes mellitus and large-for-gestational-age newborns by lifestyle counseling: a cluster-randomized controlled trial. PLoS Med 2011, 8:e1001036.PubMedView Article
            44. Nascimento SL, Surita FG, Parpinelli MA, Siani S, Pinto e Silva JL: The effect of an antenatal physical exercise programme on maternal/perinatal outcomes and quality of life in overweight and obese pregnant women: a randomised clinical trial. BJOG 2011, 118:1455–1463.PubMedView Article
            45. Dodd JM, Grivell RM, Crowther CA, Robinson JS: Antenatal interventions for overweight or obese pregnant women: a systematic review of randomised trials. BJOG 2010, 117:1316–1326.PubMedView Article
            46. Streuling I, Beyerlein A, von Kries R: Can gestational weight gain be modified by increasing physical activity and diet counseling? A meta-analysis of interventional trials. Am J Clin Nutr 2010, 92:678–687.PubMedView Article
            47. Tanentsapf I, Heitmann BL, Adegboye AR: Systematic review of clinical trials on dietary interventions to prevent excessive weight gain during pregnancy among normal weight, overweight and obese women. BMC Pregnancy Childbirth 2011, 11:81.PubMedView Article
            48. Sui Z, Grivell RM, Dodd JM: Antenatal exercise to improve outcomes in overweight or obese women: a systematic review. Acta Obstet Gynecol Scand 2012, 91:538–545.PubMedView Article
            49. Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gotzsche PC, Ioannidis JP, Clarke M, Devereaux PJ, Kleijnen J, Moher D: The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. BMJ 2009, 339:b2700.PubMedView Article
            50. Cochrane Handbook for Systematic Reviews of Interventions [http://​www.​cochrane.​org/​training/​cochrane-handbook] 2011.
            51. Olson CM: A call for intervention in pregnancy to prevent maternal and child obesity. Am J Prev Med 2007, 33:435–436.PubMedView Article
            52. Kinnunen TI, Pasanen M, Aittasalo M, Fogelholm M, Hilakivi-Clarke L, Weiderpass E, Luoto R: Preventing excessive weight gain during pregnancy - a controlled trial in primary health care. Eur J Clin Nutr 2007, 61:884–891.PubMedView Article
            53. Claesson IM, Brynhildsen J, Cedergren M, Jeppsson A, Sydsjo A, Josefsson A: Weight gain restriction during pregnancy is safe for both the mother and neonate. Acta Obstet Gynecol Scand 2009, 88:1158–1162.PubMedView Article
            54. Michie S, Abraham C, Eccles MP, Francis JJ, Hardeman W, Johnston M: Strengthening evaluation and implementation by specifying components of behaviour change interventions: a study protocol. Implement Sci 2011, 6:10.PubMedView Article
            55. Olson CM: Achieving a healthy weight gain during pregnancy. Annu Rev Nutr 2008, 28:411–423.PubMedView Article
            56. Birdsall KM, Vyas S, Khazaezadeh N, Oteng-Ntim E: Maternal obesity: a review of interventions. Int J Clin Pract 2009, 63:494–507.PubMedView Article
            57. Gardner B, Wardle J, Poston L, Croker H: Changing diet and physical activity to reduce gestational weight gain: a meta-analysis. Obes Rev 2011, 12:e602-e620.PubMedView Article
            58. Craig P, Dieppe P, Macintyre S, Michie S, Nazareth I, Petticrew M: Developing and evaluating complex interventions: the new Medical Research Council guidance. BMJ 2008, 337:a1655.PubMedView Article
            59. Quinlivan JA, Lam LT, Fisher J: A randomised trial of a four-step multidisciplinary approach to the antenatal care of obese pregnant women. Aust NZJ Obstet Gynaecol 2011, 51:141–146.View Article
            60. Pre-publication history

              1. The pre-publication history for this paper can be accessed here:http://​www.​biomedcentral.​com/​1741-7015/​10/​47/​prepub

            Copyright

            © Oteng-Ntim et al; licensee BioMed Central Ltd. 2012