GDM: Postpartum Care (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To assess:

  • To what extent GDM women developed type 2 diabetes later in life
  • To what extent that development could be predicted
  • If the impaired carbohydrate metabolism was related to other aspects of the metabolic syndrome.
Inclusion Criteria:

Cases: All women who were diagnosed with GDM in 1984-1985 and gave birth in southern Stockholm were sampled from the Swedish medical register

Controls: 150 women at random (every fifth woman) from the Stockholm Pregnancy and Women's Nutrition study

Exclusion Criteria:
Type 1 DM at pregnancy (n=6)
Description of Study Protocol:

Recruitment

Swedish national registry (28 of 58 cases agreed to participate, 52 of 160 controls agreed to participate)

Design Women asked to come to Obesity unit 15 years after index pregnancy for OGTT and measurement of covariates.

Blinding used (if applicable)

Diagnosis by OGTT

Intervention (if applicable):  Not applicable

Statistical Analysis - t test, chi-squared test, Kaplan-Meier

 

Data Collection Summary:

Timing of Measurements

15 years following pregnancy in 1984-1985.

Dependent Variables

  • GDM - 1984-5 case/control status from Swedish medical records (as diagnosed by abnormal urine test + 2 hour OGTT with 75g glucose having 2 values over 9mmol/L)

Independent Variables

  • Diabetes - OGTT with 75 g glucose after a night of at least 8 hours of fasting. Diabetes diagnosis if the women had a 2 hour blood-glucose value over 10 mmol/L. Blood was sampled immediately before the glucose load for fasting glucose, insulin and liver tests and other routine lab samples. Glucose was sampled every 30 minutes for 2 hours; on the first and last occasion, blood insulin was also measured.

Control Variables

  • Weight was measured in light underwear on a scale which was regularly calibrated to the nearest 0.1 kg (Tarya TBF 305, Tokyo, Japan)
  • Height was measured to the nearest centimetre.
  • Fat mass was measured by bio-impedance (Tarya TBF 305).
  • Subjects were asked to fill in questionnaires about diet, exercise habits, social conditions, medical history and questions about their knowledge of risk for type 2 diabetes mellitus.
Description of Actual Data Sample:

Initial N: 28 cases and 52 controls

Attrition (final N): as above

Age: mean: 47.6 +/- 4.2 for cases, 45.6 +/- 4.7 for controls

Ethnicity: Swedish, not further specified

Other relevant demographics

Anthropometrics: BMI, waist/hip ratio, and waist circumference did not significantly differ between cases and controls. On average, GDM cases had more children 2 +/- 0.9 vs. 2.4 +/- 0.6. Menopausal status did not significantly differ between groups

Location: Obesity unit in Stockholm, Sweden

 

Summary of Results:

Table 1. Clinical data of 15 years of follow up of women who were diagnosed with GDM during a pregnancy 1984–1985 compared with matched control group. Values are mean (SD). Image

 *ns - t-test

**chi-squared test

Other Findings

  • Mean BMI in the diabetic group was 27.4 kg/m2 and in the non-diabetic GDM group 24.6 kg/m2 (P < 0.05)
  • The mean weight gain since the first child was 8.4 kg in all GDM versus 8.1 kg in controls (ns). The women who developed type 2 diabetes mellitus, however, gained 15.1 kg since the birth of their first child (P < 0.05).
  • Blood pressure and serum lipids did not significantly differ between cases who developed diabetes compared to cases who didn't develop diabetes
  • 54% of GDM women unaware they had a higher risk of type 2 diabetes than others

 

Author Conclusion:

Women who are diagnosed with GDM have a considerably higher risk of developing type 2 diabetes mellitus later in life. Despite a close medical monitoring during pregnancy, the further follow up within the health care system and information about long term consequences of GDM for later type 2 diabetes mellitus development seems to be generally lacking. More active strategies for future weight control and lifestyle advice after delivery might therefore be indicated for women with GDM.

Funding Source:
University/Hospital: Huddinge University Hospital
Reviewer Comments:

As authors noted, there were low participation rates (~50% for cases, 33% for controls) - did not differ in age for cases and age, weight for controls but don't know about other possible selection factors. But even if all 58 women had participated and none of the remaining women turned out to have type 2 diabetes mellitus, the percentage of the type 2 diabetes mellitus had still been 17% versus 0% in the control group.

Unclear how many women declined versus could not be reached; also don't know reason for declining participation

Sample size for comparison between GDM cases who developed diabetes compared to those who didn't was small (n=28) and no power calculations provided; would have been good to report confidence intervals or P values for lipids, bp, etc 

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes