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Deflation of gastric band balloon in pregnancy for improving outcomes

  1. Amanda E Jefferys1,*,
  2. Dimitrios Siassakos2,
  3. Tim Draycott1,
  4. Valentine A Akande3,
  5. Robert Fox4

Editorial Group: Cochrane Pregnancy and Childbirth Group

Published Online: 30 APR 2013

Assessed as up-to-date: 29 OCT 2012

DOI: 10.1002/14651858.CD010048.pub2


How to Cite

Jefferys AE, Siassakos D, Draycott T, Akande VA, Fox R. Deflation of gastric band balloon in pregnancy for improving outcomes. Cochrane Database of Systematic Reviews 2013, Issue 4. Art. No.: CD010048. DOI: 10.1002/14651858.CD010048.pub2.

Author Information

  1. 1

    North Bristol NHS Trust, Department of Women's Health, Bristol, UK

  2. 2

    University of Bristol, School of Clinical Sciences, Bristol, UK

  3. 3

    Directorate of Women's Health, Obstetrics & Gynaecology, Bristol, England, UK

  4. 4

    Taunton and Somerset NHS Trust, Department of Women's Health, Taunton, Somerset, UK

*Amanda E Jefferys, Department of Women's Health, North Bristol NHS Trust, Southmead Hospital, Southmead Road, Westbury-on-Trym, Bristol, BS10 5NB, UK. ajefferys@doctors.org.uk.

Publication History

  1. Publication Status: New
  2. Published Online: 30 APR 2013

SEARCH

 

Background

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

As the prevalence of obesity increases, so too has the use of bariatric (weight-loss) surgery, including laparoscopic adjustable gastric banding (LAGB). With women of reproductive age accounting for 49% of all those undergoing surgery (Maggard 2008), increasing numbers of women who have undergone this procedure are becoming pregnant. There are concerns about tolerability in pregnancy and the effect on maternal nutrition and body weight (Guelinckx 2009).

 

Description of the condition

Obesity is associated with poor health. Maternal obesity (defined as a body mass index (BMI) of equal to or greater than 30 in pregnancy), especially extreme obesity (BMI of equal to or greater than 50), is associated with higher rates of adverse pregnancy outcomes including gestational diabetes (odds ratio (OR) for extremely obese 15.7, 95% confidence interval (CI) 4.75 to 51.8) (CMACE 2010; CMACE 2011; Knight 2010), hypertensive disorders (OR 7.35, 95% CI 3.07 to 17.6 for nulliparous women with extreme obesity) (CMACE 2010; CMACE 2011; Knight 2010), reduced mobility and thromboembolism (CMACE 2010; CMACE 2011), delivery by caesarean section (OR 3.50, 95% CI 2.72 to 4.51) (CMACE 2010; Knight 2010; Usha Kiran 2005), postpartum haemorrhage (OR 1.5, 95% CI 1.2 to 1.8) (CMACE 2010; CMACE 2011; Usha Kiran 2005), fetal macrosomia (birthweight greater than 4.5 kg) (OR 5.23, 95% CI 2.81 to 9.74) (Knight 2010; Usha Kiran 2005), congenital malformations (including neural tube defects (OR 1.87, 95% CI 1.62 to 2.15), cardiovascular abnormalities (OR 1.30, 95% CI 1.12 to 1.51), and orofacial clefts (OR 1.20, 95% CI 1.03 to 1.40) (Stothard 2009), stillbirth (Salihu 2011) and maternal mortality (CMACE 2011). It has been reported that limiting gestational weight gain to less than 15 lb (approximately 7 kg) might reduce the incidence of adverse outcomes (Guelinckx 2009; Jensen 2005; Kiel 2007), but the evidence supporting this is not conclusive (Dodd 2010), and any limitation of gestational weight gain has to be balanced against the potential harms.

 

Description of the intervention

LAGB is a well-established treatment for extreme obesity (Colquitt 2009) with proven safety and efficacy in achieving significant weight loss and improved health (Chapman 2004). The procedure involves laparoscopic placement of an adjustable band containing a fluid-filled balloon around the upper portion of the stomach. This band acts to reduce stomach capacity, by creating a small upper stomach pouch and limiting passage of food into the lower digestive portion of the stomach, resulting in early satiation; aiding weight loss by reducing food intake. The volume of the balloon can be adjusted by addition or removal of fluid through a subdermal port positioned at the time of surgery. In this way nutritional intake, and thus body weight, can be influenced. Potential maternal and perinatal benefits of limiting weight gain in pregnancy have to be set against theoretical risks of leaving the balloon inflated. The reduction in nutritional intake from an inflated gastric band balloon might have adverse consequences. In general, reduced nutritional intake and low maternal weight gain are known to be associated with lower birthweight (OR 1.66, 95% CI 1.44 to 1.92) (Guelinckx 2009; Stotland 2006; Strauss 1999), and preterm labour (although this was a more significant finding in underweight ((OR 6.7, 95% CI 1.1 to 40.6) and normal-weight (OR 3.6, 95% CI 1.6 to 8.0) women than overweight women (OR 1.6, 95% CI 0.7 to 3.5)) (Schieve 2000). Similarly, a systematic review did not find limiting gestational weight gain to be associated with small-for-gestational age in obese and overweight women (Siega-Riz 2009). Recognised complications of LAGB also include gastric perforation, gastric necrosis, gastric prolapse, band leakage, and band migration and slippage (Chevallier 2004; Forsell 1999). The incidence of band migration and slippage of the band is increased in pregnancy because of raised intra-abdominal pressure (Guelinckx 2009). Band migration often presents with nausea and vomiting and as these are common in normal early pregnancy, so band migration might go unrecognised initially, resulting in avoidable significant maternal morbidity. For these reasons, many advocate routine deflation of the band balloon at the beginning of pregnancy, but this might later result in excessive maternal weight gain and its associated complications, such as pregnancy complications (hypertensive disorders, gestational diabetes) (OR 2.10, 95% CI 1.74 to 2.54), caesarean delivery (OR 1.29, 95% CI 1.09 to 1.54) and increased birthweight (weight difference 206.45 g, 95% CI 178.82 to 234.08) (Mamun 2011).

Because of the controversy over appropriate gestational weight gain and concerns over band complications, management of gastric bands in pregnancy is inconsistent. Some clinicians advocate deflation of the gastric band balloon for the entire pregnancy allowing sufficient intake of nutrients to allow for fetal growth and development and potentially reducing the risk of band complications. This might, however, result in excessive gestational weight gain (defined by Institute of Medicine 2009 as 20 lbs or 9 kg for obese women) and its associated complications (Mamun 2011). Others promote a policy of leaving the balloon inflated for the duration of pregnancy with deflation only if significant complications such as band migration or severe nausea and vomiting occur (Lapolla 2010; Sheiner 2009). Another approach that has been employed is to deflate the balloon in the early part of pregnancy with re-inflation at the beginning of the second or third trimesters (Dixon 2001), or selective adjustment of the balloon according to tolerance and gestational weight gain (Carelli 2011; Dixon 2005; Martin 2000; Skull 2004; Weiss 2001). These approaches might reduce the risk of aggravating symptoms of nausea and vomiting in early pregnancy and allow sufficient intake of crucial micronutrients during organogenesis, and yet still limit excessive gestational weight gain and its associated complications in later pregnancy.

 

How the intervention might work

Leaving the balloon deflated throughout pregnancy would allow sufficient intake of nutrients for maternal and fetal health while potentially reducing the rate of nausea and vomiting and more serious complications such as band slippage and nutritional deficiencies.

Maintaining inflation of the balloon for the duration of pregnancy might limit gestational weight gain (Carelli 2011), and so reduce adverse maternal and perinatal outcomes (CMACE 2010).

 

Why it is important to do this review

With the growing prevalence of obesity, the incidence of pregnant women who have undergone LAGB procedures is increasing (Maggard 2008). Currently, no guidance exists for maternity healthcare workers on how best to manage gastric bands to achieve optimum maternal and neonatal outcomes (Maggard 2008).

 

Objectives

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

To compare maternal and perinatal outcomes for elective gastric band balloon deflation versus intention to leave the balloon inflated during pregnancy.

 

Methods

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Criteria for considering studies for this review

 

Types of studies

According to the study protocol (Jefferys 2012), only randomised, quasi-randomised, and cluster-randomised controlled trials were eligible for inclusion in the review. Multi-arm studies were also considered. We intended to include studies presented only as abstracts and to explore their impact in a sensitivity analysis. Abstracts were assessed in the same way as full papers. We planned to include abstracts in the main meta-analysis if there was sufficient information presented in the abstract to demonstrate that it met the review's inclusion criteria and was of an acceptable methodological standard. We planned to exclude studies (with a note in the excluded studies table explaining that these studies would be reconsidered for inclusion once the full publication becomes available, or once the authors have provided more information) if there were doubts about the eligibility of the study or if it was thought to be at risk of serious bias, for example, in terms of randomisation methods, withdrawals or post-randomisation exclusions.

 

Types of participants

Pregnant women who have previously undergone adjustable gastric banding, with the band still inflated.

 

Types of interventions

Studies comparing elective deflation of the gastric band balloon in different trimesters of pregnancy or throughout versus intention to leave the balloon inflated for the duration of pregnancy.

 

Types of outcome measures

The outcome measures included in our review have been short-listed on the basis of being meaningful to clinicians, public, and policy makers, and have been discussed and agreed with a Maternity Service User Panel of six lay women.

 

Primary outcomes

 
Maternal

  • Gestational diabetes (as defined by individual trial)
  • Hypertensive disorders of pregnancy (pregnancy-induced hypertension and/or pre-eclampsia)
  • Postpartum haemorrhage (as defined by individual trial)
  • Tolerance to intervention (nausea/vomiting)

 
Neonatal

  • Admissions to neonatal unit

We intended to include primary outcomes in the 'Summary of findings' table.

 

Secondary outcomes

 
Maternal

  • Maternal weight gain during pregnancy (average (5 kg to 9 kg), % excessively high (greater than 9 kg), % excessively low (below 5 kg)) as defined by Institute of Medicine 2009)
  • Mode of birth (normal birth, operative vaginal birth, caesarean birth)
  • Maternal admission to hospital for any reason in the antenatal and postnatal period (up to six completed weeks)
  • Venous thromboembolism in the antenatal and postnatal period (up to six completed weeks)
  • Anaemia in pregnancy (haemoglobin (Hb) less than 11% (WHO 2001); or as defined by individual trial)
  • Actual balloon status in each trimester (remained inflated, or was deflated for maternal preference or clinical reasons, or re inflated) (if stated)

 
Fetal/neonatal

  • Two-year survival-free disability
  • Low Apgar score (less than seven at five minutes)
  • Preterm birth (less than 37 completed weeks): a. spontaneous b. iatrogenic c. total
  • Extremely preterm birth (less than 28 completed weeks)
  • Birthweight
  • Large-for-gestational age (birthweight greater than 90th centile; or as defined by individual trial)
  • Macrosomia (greater than 4000 g; or as defined by individual trial)
  • Small-for-gestational age (birthweight smaller than 10th centile; or as defined by individual trial)
  • Stillbirth
  • Early neonatal death (first seven days)
  • Perinatal mortality (stillbirth and early neonatal death (WHO))
  • Congenital malformations (orofacial clefts, cardiac septal defects, neural tube defects)

 

Search methods for identification of studies

 

Electronic searches

An electronic search was performed as per the review protocol (Jefferys 2012).

We contacted the Trials Search Co-ordinator to search the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2012). 

The Cochrane Pregnancy and Childbirth Group's Trials Register is maintained by the Trials Search Co-ordinator and contains trials identified from:

  1. monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
  2. weekly searches of MEDLINE;
  3. weekly searches of EMBASE;
  4. handsearches of 30 journals and the proceedings of major conferences; and
  5. weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Details of the search strategies for CENTRAL, MEDLINE and EMBASE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the 'Specialized Register' section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described above are each assigned to a review topic (or topics). The Trials Search Co-ordinator searches the register for each review using the topic list rather than keywords. 

In addition, we searched the Web of Science database (1940 to September 2012) using the search strategy detailed in Appendix 1.

 

Searching other resources

We planned to search reference lists of retrieved studies.

We did not apply any language restrictions.

 

Data collection and analysis

 

Selection of studies

Two review authors (A Jefferys (AJ) and D Siassakos (DS)) independently assessed for inclusion all the potential studies we identified as a result of the search strategy. Any disagreements were resolved through discussion and, if required, we planned to consult a third assessor (R Fox (RF)).

There are no included studies. Methods of data extraction and management (as detailed in our protocol (Jefferys 2012)) will be used in future updates of this review, as more data become available, see Appendix 2.

 

Results

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Description of studies

 

Results of the search

The results of the search are summarised in the study flow diagram Figure 1. The search of the Cochrane Pregnancy and Childbirth Group's Trials Register retrieved no studies. The Web of Science generated six citations. All of these were excluded on review of the abstracts - the decision was unanimous.

 FigureFigure 1. Study flow diagram.

 

Included studies

No studies met the criteria for inclusion in the review.

 

Excluded studies

Six studies were excluded at the stage that the abstracts were reviewed (one letter, three retrospective analysis of revision rates following pregnancy, one assessing outcomes in adolescents following banding (excluded as the participants were not pregnant), one analysis of nutrient deficiency post gastric bypass (excluded as participants were not pregnant and they had undergone gastric bypass rather than gastric banding)).

 

Risk of bias in included studies

No studies met the criteria for inclusion in the review, therefore, no assessment of bias was required.

 

Effects of interventions

No studies met the criteria for inclusion in the review, therefore, no conclusion can be drawn as to the effect of balloon deflation or maintaining inflation of the balloon.

 

Discussion

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Summary of main results

Our search found no randomised controlled trials to date comparing elective deflation of laparoscopic adjustable gastric banding in pregnancy versus intention to maintain balloon inflation. It is therefore unknown whether it is better to routinely deflate a gastric band balloon in pregnancy or to maintain balloon inflation with respect to maternal and neonatal outcomes.

 

Overall completeness and applicability of evidence

A full search for randomised controlled trials was performed. Although case series and case-control studies addressing band management in pregnancy exist, these are not eligible for inclusion in this review.

 

Agreements and disagreements with other studies or reviews

There are no other reviews addressing this issue.

 

Authors' conclusions

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

 

Implications for practice

At present, there is no evidence to favour either elective deflation or maintaining gastric band balloon inflation in pregnancy. This lack of evidence is reflected in the wide variation in management of the gastric band in pregnancy which is seen in observational studies (Carelli 2011; Dixon 2001; Dixon 2005; Lapolla 2010; Sheiner 2009). Management decisions regarding band status in pregnancy should continue to be made according to the clinical context. Maternal weight at the beginning of pregnancy, nausea and vomiting, tolerability of the band, gestational weight gain, fetal growth, maternal wishes, and pregnancy complications should probably all be taken into account, but this review has not produced evidence to guide practice. Issues surrounding management of the gastric band should be discussed with women who should be involved in management decisions. Close surveillance of both mother and fetus should continue throughout pregnancy to identify any complications at an early stage (Guelinckx 2009). Effective care requires communication between all members of the multidisciplinary team including obstetricians, bariatric surgeons, bariatric physicians, dieticians and midwives.

 
Implications for research

As the prevalence of obesity is predicted to rise, so too the incidence of pregnancies following laparoscopic adjustable gastric banding is likely to increase. As the optimal management of women with a gastric band in pregnancy is unknown, there is a need for further research in this area to guide clinicians and pregnant women. This review supports the need for a randomised controlled trial in the area. A systematic review of observational studies could improve our understanding of gastric band management and help to design a randomised controlled trial. A randomised controlled trial would need to have three comparison arms to reflect current practice; elective deflation of the band balloon at the beginning of pregnancy, intention to leave the balloon inflated for the duration of pregnancy, and deflation of the balloon at the beginning of pregnancy with re inflation during the second trimester. Outcome measures should mirror those we intended to assess in this review, as they are both clinically important and meaningful to clinicians and patients (outcomes were selected as important for this review by a Maternity Service User Panel). Such a randomised controlled trial would need to be sufficiently powered to detect differences in primary maternal and perinatal outcomes for different forms of band management. Any bias should be minimised by adequate randomisation using random sequence generation, concealment of allocation to participants, study personnel and outcome assessors.

 

Acknowledgements

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

We are grateful to Cathy Winter, National Institute for Health Research (NIHR) Western Comprehensive Learning Research Network (WCLRN) Research Midwife Coordinator, for setting up and co-ordinating the Maternity Service User Panel.

As part of the pre-publication editorial process, this review has been commented on by two peers (an editor and referee who is external to the editorial team), a member of the Pregnancy and Childbirth Group's international panel of consumers and the Group's Statistical Adviser.

 

Data and analyses

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

This review has no analyses.

 

Appendices

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Appendix 1. Web of Science search strategy

The following strategy will be followed for a Web of Science search:

Timespan: All years

Searches using the following terms will be performed on the database:

Search #1:  Pregnancy*

Search #2: Pregnant OR Pregnant women*

Search #3: Antenatal OR Prenatal

Search #4: Gestational

Search #5: Obstetric or Obstetrics*

Search #6: Search #1 OR Search #2 OR Search #3 OR Search #4 OR Search #5

Search #7: Gastric band

Search #8: Gastric banding

Search #9: Bariatric OR Bariatrics*

Search #10: Gastric balloon*

Search #11: Lapband

Search #12: LAGB

Search #13: Obesity surgery

Search #14: Search #7 OR Search #8 OR Search #9 OR Search #10 OR Search #11 OR Search #12 OR Search #13

Search #15: Revise OR Revision OR Revised

Search #16: Deflate OR Deflation OR Deflating

Search #17: Search #15 OR Search # 16

Search #18: Search #17 AND Search #14 AND Search#6

 * MeSH terms

 

Appendix 2. Methods of data collection and analysis to be used in future updates of this review

 

Data collection and analysis

 

Selection of studies

Two review authors (AJ and DS) will independently assess for inclusion all the potential studies we identify as a result of the search strategy. We will resolve any disagreement through discussion and, if required, we will consult a third assessor (RF).

 

Data extraction and management

We have designed a form to extract data (available upon request from DS). For eligible studies, two review authors (AJ and DS) will extract the data using the agreed form. We will resolve discrepancies through discussion or, if required, we will consult a third review author (RF). We will enter data into Review Manager software (RevMan 2011), and check them for accuracy.

When information regarding any of the above is unclear, we will attempt to contact authors of the original reports to provide further details.

 

Assessment of risk of bias in included studies

Two review authors (AJ and DS) will independently assess risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We will resolve any disagreement by discussion or by involving a third assessor (RF).

 

(1) Random sequence generation (checking for possible selection bias)

We will describe for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

We will assess the method as:

  • low risk of bias (any truly random process, e.g. random number table; computer random number generator);
  • high risk of bias (any non-random process, e.g. odd or even date of birth; hospital or clinic record number); or
  • unclear risk of bias.   

 

(2) Allocation concealment (checking for possible selection bias)

We will describe for each included study the method used to conceal allocation to interventions prior to assignment and will assess whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

We will assess the methods as:

  • low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
  • high risk of bias (open random allocation; unsealed or non-opaque envelopes, alternation; date of birth); or
  • unclear risk of bias.   

 

(3.1) Blinding of participants and personnel (checking for possible performance bias)

We will describe for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We will consider that studies are at low risk of bias if they were blinded, or if we judge that the lack of blinding would be unlikely to affect results. We will assess blinding separately for different outcomes or classes of outcomes.

We will assess the methods as:

  • low, high or unclear risk of bias for participants; or
  • low, high or unclear risk of bias for personnel.

For instances of partial blinding three assessors (AJ, DS, RF) will together assess the risk of bias.

 

(3.2) Blinding of outcome assessment (checking for possible detection bias)

We will describe for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We will assess blinding separately for different outcomes or classes of outcomes. We will assess methods used to blind outcome assessment as low, high or unclear risk of bias.

 

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

We will describe for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We will state whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information is reported, or can be supplied by the trial authors, we will re-include missing data in the analyses.

We will assess methods as:

  • low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
  • high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; 'as treated' analysis done with substantial departure of intervention received from that assigned at randomisation); or
  • unclear risk of bias.

For studies with missing data in up to 20% of participants, three assessors (AJ, DS, RF) will agree whether bias was low or high, separately for each outcome.

 

(5) Selective reporting (checking for reporting bias)

We will describe for each included study how we investigated the possibility of selective outcome reporting bias, including the databases and registries we searched for study protocols. We will record and report what we found using a matrix of outcomes; comparing each study to its protocol and other studies.

We will assess the methods as:

  • low risk of bias (where it is clear that all of the study's pre-specified outcomes, as registered in the study protocol, and all expected outcomes of interest to the review have been reported);
  • high risk of bias (where not all the study's pre-specified outcomes have been reported; one or more reported primary outcomes were not pre-specified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported); or
  • unclear risk of bias.

 

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

We will describe for each included study any important concerns we have about other possible sources of bias, including: early discontinuation, baseline imbalances, post-hoc changes to the protocol, outcome assessors not being independent from the researchers.

We will assess for each of these whether each study was free of relevant problems that could put it at risk of bias:

  • low risk of other bias;
  • high risk of other bias; or
  • unclear risk.

 

(7) Bias relevant to cluster designs

We will also assess cluster trials for bias specific to cluster designs, and determine whether the risk of bias was low, high or unclear.

We will specifically assess for:

  • recruitment to the trial after the clusters have been randomised;
  • baseline imbalances between the randomised clusters;
  • missing clusters; and
  • analysis without taking clustering into account.

To account for 'herd effects' and to determine the impact of contamination in non-cluster trials, we will conduct sensitivity analysis with and without cluster trials.

 

(8) Bias relevant to multiple-arm designs

We will also assess multiple-arm trials for specific bias, and determine whether the risk of bias was low, high or unclear.

We will specifically assess for:

  • presentation of data for each of the groups to which participants were randomised; and
  • evidence of selective reporting of comparisons of intervention arms for some of the outcomes.

 

(9) Overall risk of bias

We will make explicit judgements about whether studies are at high risk of bias, according to specific criteria given in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). With reference to the bias domains above, we will assess the likely magnitude and direction of the bias and whether we consider it is likely to impact on the findings. We will explore the impact of the level of bias through undertaking sensitivity analysis.

 

Measures of treatment effect

 

Dichotomous data

For dichotomous data, we will present results as summary risk ratio with 95% confidence intervals. 

 

Continuous data

For continuous data, we will use the mean difference if outcomes are measured in the same way between trials. We will use methods described in section 7.7.3 of the Cochrane Handbook for Systematic Reviews of Interventions to obtain or calculate standard deviations (Higgins 2011). We will use the standardised mean difference to combine trials that measure the same outcome, but use different methods.  

We will not address ordinal outcome measures in our review.

 

Unit of analysis issues

 

Cluster-randomised trials

We will include cluster-randomised trials in the analyses along with individually-randomised trials. We will adjust their sample sizes using the methods described in the Cochrane Handbook for Systematic Reviews of Interventions using an estimate of the intracluster correlation co-efficient (ICC) derived from the trial (if possible), from a similar trial, or from a study of a similar population (Higgins 2011). If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster-randomised trials and individually-randomised trials, we plan to synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the study designs and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely.

We will also acknowledge heterogeneity in the randomisation unit and perform a sensitivity analysis to investigate the effects of the randomisation unit.

 

Cross-over trials

We will exclude cross-over designs.

 

Multiple pregnancies

We will use the methods recommended by the Pregnancy and Childbirth Group Methodological Guidelines and the Cochrane Handbook for Systematic Reviews of Interventions (sections 9.3.7 and 16.3) to analyse data relating to multiple pregnancies (Higgins 2011). We will use the number of women as denominator for maternal outcomes and the number of babies as denominator for neonatal outcomes.

We will use cluster-trial methods, treating multiple pregnancies as clusters, only if the proportion of multiple pregnancies in a trial is substantial (greater than 20%). Otherwise, we will analyse data as if babies from multiple pregnancies are independent.

 

Dealing with missing data

For included studies, we will note levels of attrition.

For all outcomes, we will carry out analyses, as far as possible, on an intention-to-treat basis, i.e. we will attempt to include all participants randomised to each group in the analyses, and all participants will be analysed in the group to which they were allocated, regardless of whether or not they received the allocated intervention.

Where there are missing data, the denominator for each outcome in each trial will be the number randomised minus any participants whose outcomes are known to be missing ('available case analysis'). We will explore the impact of including studies with relatively (less than 20%) high levels of missing data in the overall assessment of treatment effect by using sensitivity analysis. For example, we will explore 'worst case' scenarios of all missing participants having a specific outcome.

We will exclude from the analyses data from trials or outcomes that are at high risk of bias, e.g. those with very high levels of missing data (greater than 20%) or trials analysed 'per treatment received' with a large number of participants analysed in the wrong group (greater than 20%). Before exclusion, we will attempt to use data from the trial report, or from personal communication with the trial investigators, to restore participants to the correct group.

 

Assessment of heterogeneity

We will assess statistical heterogeneity in each meta-analysis using the T2, I2 and Chi2 statistics. We will regard heterogeneity as substantial if the I2 is greater than 30% and either the T2 is greater than zero, or there is a low P value (less than 0.10) in the Chi2 test for heterogeneity, or there is obvious inconsistency between trials in direction or magnitude of effects (judged visually).

 

Assessment of reporting biases

If there are 10 or more studies in the meta-analysis, we will investigate reporting biases (such as publication bias) using funnel plots. We will assess funnel plot asymmetry visually, and use formal tests for funnel plot asymmetry. For continuous outcomes, we will use the test proposed by Egger 1997, and for dichotomous outcomes we will use the test proposed by Harbord 2006. If asymmetry is detected in any of these tests or is suggested by a visual assessment, we will perform exploratory analyses to investigate possible causes; for example, by comparing fixed-effect and random-effects estimates, treatment effects from large and small studies, or effects from studies with low and high risk of bias.

 

Data synthesis

We will carry out statistical analysis using RevMan 2011. We will use fixed-effect meta-analysis for combining data where it is reasonable to assume that studies are estimating the same underlying treatment effect: where trials are examining the same intervention, and the trials' populations and methods are judged sufficiently similar. If there is clinical heterogeneity sufficient to expect that the underlying treatment effects differ between trials, or if substantial statistical heterogeneity is detected, we will use random-effects meta-analysis to produce an overall summary. The results will be presented as the average treatment effect with 95% confidence intervals, and the estimates of  T2 and I2. The random-effects summary will be treated as the average range of possible treatment effects and we will discuss the clinical implications of treatment effects differing between trials.

 

Subgroup analysis and investigation of heterogeneity

If there is an adequate number of studies and we identify substantial heterogeneity, we will investigate it using subgroup analyses and sensitivity analyses. We will consider whether an overall summary is meaningful, and if it is, use random-effects analysis to produce it.

We plan to explore in subgroup analyses at study level.

  1. Timing of conception: conception within one year of surgery versus conception beyond one year of surgery.
  2. Pre-existing diabetes: presence of pre-existing diabetes versus absence of pre-existing diabetes.
  3. Studies with routine deflation throughout pregnancy versus studies with selective deflation in the first, second, or third trimester of pregnancy. We will use multiple-treatments meta-analysis to compare different types of deflation.

The following primary outcomes will be used in subgroup analyses as appropriate.

 

Maternal

  • Gestational diabetes (excluding for subgroup analysis 2)
  • Hypertensive disorders of pregnancy
  • Maternal admission to hospital
  • Tolerance to intervention

 

Fetal

  • Admissions to neonatal unit

We will assess differences between subgroups by interaction tests. We will present results quoting the Χ2, I2, and P values. We will treat subgroup analysis as exploratory.

 

Sensitivity analysis

We will perform a sensitivity analysis in cases of statistical heterogeneity. We will also perform a sensitivity analysis by trial quality, separating trials into those with high (e.g. quasi-randomised, studies published only as abstracts or without peer review) and low risk of bias, and with or without the inclusion of cluster-randomised trials. Finally, we will also conduct sensitivity analysis to explore the effects of fixed-effect or random-effects analysis for outcomes with statistical heterogeneity and the effects of any assumptions made such as the value of the ICC used for cluster-randomised trials.

The following primary outcomes will be used in sensitivity analyses as appropriate.

 

Maternal

  • Gestational diabetes (excluding for subgroup analysis 2)
  • Hypertensive disorders of pregnancy
  • Maternal admission to hospital
  • Tolerance to intervention

 

Fetal

  • Admissions to neonatal unit

 

Contributions of authors

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Amanda Jefferys

  • Contact author
  • Drafting of protocol
  • Performing secondary search
  • Drafting of review

 

Dimitrios Siassakos

  • Guarantor
  • Conceiving the review
  • Methodology
  • Drafting of protocol
  • Drafting of review

 

Robert Fox

  • Conceiving the review
  • Coordinating the review
  • Editing of protocol
  • Editing of review

 

Valentine Akande

  • Providing general advice on review
  • Editing of protocol
  • Editing of review

 

Timothy Draycott

  • Co-ordinating the review
  • Providing general advice on protocol and review
  • Editing of review

 

Declarations of interest

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

The authors are involved in a national surveillance study (UKOSS) of the management of gastric banding in pregnancy, which would not be eligible for inclusion in this systematic review. They have no known conflict of interest.

 

Sources of support

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms
 

Internal sources

  • No sources of support supplied

 

External sources

  • National Institute for Health Research (NIHR) Western Comprehensive Learning Research Network (WCLRN), UK.
    Funding for the Maternity Patient Panel to collaborate in research proposals

 

Differences between protocol and review

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Results
  6. Discussion
  7. Authors' conclusions
  8. Acknowledgements
  9. Data and analyses
  10. Appendices
  11. Contributions of authors
  12. Declarations of interest
  13. Sources of support
  14. Differences between protocol and review
  15. Index terms

There was no change in methodology between the protocol and the review.

References

Additional references

  1. Top of page
  2. AbstractRésumé
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Data and analyses
  11. Appendices
  12. Contributions of authors
  13. Declarations of interest
  14. Sources of support
  15. Differences between protocol and review
  16. Additional references
Carelli 2011
  • Carelli AM, Ren CJ, Youn HA, Friedman EB, Finger AE, Lok BH, et al. Impact of laparoscopic adjustable gastric banding on pregnancy, maternal weight, and neonatal health. Obesity Surgery 2011;21(10):1552-8.
Chapman 2004
  • Chapman AE, Kiroff G, Game P, Foster B, O'Brien P, Ham J, et al. Laparoscopic adjustable gastric banding in the treatment of obesity: a systematic literature review. Surgery 2004;135(3):326-51.
Chevallier 2004
  • Chevallier J, Zinzindohoue F, Douard R, Blanche J, Berta J, Altman J, et al. Complications after laparoscopic adjustable gastric banding for morbid obesity: experience with 1000 patients over 7 years. Obesity Surgery 2004;14(3):407-14.
CMACE 2010
  • CMACE/RCOG Joint Guideline. Management of Women with Obesity in Pregnancy. London: Jointly published by the Centre for Maternal and Child Enquiries and the Royal College of Obstetricians and Gynaecologists, 2010.
CMACE 2011
  • Centre for Maternal and Child Enquiries (CMACE). Saving Mother's Lives: reviewing maternal deaths to make motherhood safer: 2006-08. The Eighth Report on Confidential Enquiries into Maternal Deaths in the United Kingdom. British Journal of Obstetrics and Gynaecology 2011;118(Suppl 1):1-203.
Colquitt 2009
Dixon 2001
Dixon 2005
Dodd 2010
Egger 1997
Forsell 1999
Guelinckx 2009
Harbord 2006
Higgins 2011
  • Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org.
Institute of Medicine 2009
  • Institute of Medicine. Weight gain during pregnancy: reexamining the guidelines. Institute of Medicine Guideline 2009.
Jefferys 2012
  • Jefferys AE, Siassakos D, Draycott T, Akande VA, Fox R. Deflation of gastric band balloon in pregnancy for improving outcomes. Cochrane Database of Systematic Reviews 2012, Issue 8. [DOI: 10.1002/14651858.CD010048]
Jensen 2005
  • Jensen DN, Ovesen P, Beck Nielsen H, Molsted-Pedersen L, Sorensen B, Vinter C, et al. Gestational weight gain and pregnancy outcomes in 481 obese glucose tolerant women. Diabetes Care 2005;28:2118-22.
Kiel 2007
Knight 2010
Lapolla 2010
  • Lapolla A, Marangon M, Dalfra MG, Segato G, De Luca M, Fedele D, et al. Pregnancy outcome in morbidly obese women before and after laparoscopic gastric banding. Obesity Surgery 2010;20(9):1251-7.
Maggard 2008
Mamun 2011
  • Mamun A, Callaway LK, O'Callaghan MJ, Williams GM, Najman J, Alati R, et al. Associations of maternal pre-pregnancy obesity, and excess pregnancy weight gains with adverse pregnancy outcomes and length of hospital stay. BMC Pregnancy & Childbirth 2011;11:62.
Martin 2000
RevMan 2011
  • The Nordic Cochrane Centre, The Cochrane Collaboration. Review Manager (RevMan). 5.1. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2011.
Salihu 2011
Schieve 2000
  • Schieve L, Cogswell M, Scanlon K, Perry G, Ferre C, Blackmore-Prince C, et al. Pre-pregnancy body mass index and pregnancy weight gain: associations with preterm delivery. Obstetrics and Gynecology 2000;96(2):194-200.
Sheiner 2009
  • Sheiner E, Balaban E, Dreiher J, Levi I, Levy A. Pregnancy outcome in patients following different types of bariatric surgeries. Obesity Surgery 2009;19(9):1286-92.
Siega-Riz 2009
  • Siega-Riz AM, Viswanathan M, Moos M, Mumford S, Knaack J, Thieda P, et al. A systematic review of outcomes of maternal weight gain according to the Institute of Medicine recommendations: birthweight, fetal growth and postpartum weight retention. American Journal of Obstetrics and Gynaecology 2009;201(4):339.
Skull 2004
  • Skull AJ, Slater GH, Duncombe JE, Fielding GA. Laparoscopic adjustable banding in pregnancy: safety, patient tolerance and effect on obesity-related pregnancy outcomes. Obesity Surgery 2004;14(2):230-5.
Stothard 2009
Stotland 2006
Strauss 1999
  • Strauss RS, Dietz WH. Low maternal weight gain in the second or third trimester increases the risk for intrauterine growth retardation. Journal of Nutrition 1999;129:988-93.
Usha Kiran 2005
Weiss 2001
WHO
  • World Health Organization. Maternal and perinatal health. http://www.who.int/maternal_child_adolescent/topics/maternal/maternal_perinatal/en/index.html (accessed 27/03/2012).
WHO 2001
  • World Health Organization. Iron deficiency anaemia: Assessment, prevention, and control. A guide for programme managers. whqlibdoc.who.int/hq/2001/WHO_NHD_01.3.pdf (accessed 01/04/2012).