GDM: Self-monitoring of Glucose (2001)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To conduct a population-based study of maternal and neonatal characteristics and delivery complications in relation to the outcome of a 75 g, 2 hour oral glucose tolerance test at 25 to 30 weeks gestation.
Inclusion Criteria:
  • Singleton pregnancy
  • Delivery at Lund Hospital
Exclusion Criteria:
  • Delivery <25 wk gestation
  • Insulin dependent diabetes upon entry into study
  • Diagnosis of GDM before 25 wk gestation
Description of Study Protocol:


January 1, 1995 to December 31, 1997 OGTT’s were performed on all pregnant women between 27 and 28 wk gestation in 4 geographic areas of southern Sweden.

Prenatal care is free in Sweden and all women in Sweden have screening for diabetes at 25-30 wk gestation.

Design:  Population-Based Descriptive Study

Blinding Used (if applicable):  not applicable

Intervention (if applicable):

  • All received device for home glucose monitoring.
  • Blood glucose was tested 6 times/d if on insulin and 6 times every other day if not on insulin. 
  • A diabetologist called every woman with GDM every wk or every other wk

Statistical Analysis

Statistical analysis was performed with the Mantel-Haenszel method after various stratifications.  Each group was compared with all other groups.  95% confidence intervals were determined by test-based method.

Data Collection Summary:

Timing of Measurements

75 g, 2 hour oral glucose tolerance test at 25 to 30 weeks gestation.

Dependent Variables

  • Method of delivery
  • Gestational age at delivery
  • Birth weight

Independent Variables

  • 75 g, 2 hour oral glucose tolerance test at 25 to 30 weeks gestation: 
  • Overnight fasting
  • 75 g glucose given, followed by a 2-hr whole blood glucose determination

Blood glucose at 2-hr:

  • Gestational diabetes:  >9 mmol/L (162 mg/dl)
  • Sub-GDM group: 7.8 to 8.9 mmol/L (140-162 mg/dl)
  • Control group: <7.8 mmol/L (140 mg/dl)

Control Variables

  • Age
  • Parity
  • Smoking habits
Description of Actual Data Sample:

Initial N:  20,865 deliveries in 4 hospitals

Attrition (final N):  as above

Age:  mean age not provided, all subjects stratified for age

Ethnicity:  not mentioned

Other relevant demographics:


Location:  Southern Sweden

Summary of Results:

Other Findings

20,865 deliveries in 4 hospitals

  • 14,078 women had OGTT (67% coverage)
  • 12,657 (93%) had OGTT 25-30 wk gestation. 
  • 4526 women with OGTT <7.8 mmol/L
  • 131 women with OGTT: 7.8 to 8.9 mmol/L
  • 116 women with GDM: >9 mmol/L
  • (1.2% had GDM)

Odds ratio for having sub-GDM in 26-28.9 BMI group 1.13 (95%, CI 0.75-1.71).

Odds ratio for having GDM with BMI 26-28.9: 2.39 (95% CI, 1.39-4.10) and for GDM with BMI >29: 3.88 (95% CI, 2.37-6.36).

40% of women treated with insulin


   Sub-GDM           GDM   Control
C-Section 13.8 18.1 7.8

<37 wk at delivery

8.4   13.8     5.7

(P<0.001 for trend)

Birthweight >4500 g  

9.9    10.3  4.5 

(P<0.001 for trend)

Author Conclusion:

We conclude that women with a 2-hr oral GTT of 7.8 to 8.9 mmol/L have an increased risk of having a nonoptimal delivery outcome. 

Women with GDM, despite having an increased BMI, were delivered of normal-size babies probably due to the intense treatment given.

Funding Source:
Reviewer Comments:

Good population study because all women in Sweden receive prenatal care and all women are screened for GDM at 25-30 wk gestation.

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? Yes
  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? Yes
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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.) N/A
  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? N/A
  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? Yes
  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? N/A
  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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  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? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? Yes
  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? N/A
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? Yes
  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)? Yes
  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? N/A
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? Yes
  10.2. Was the study free from apparent conflict of interest? Yes