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GDM: Monitoring (2008)


Langer O, Levy J, Brustman L, Anyaegbunam A, Merkatz R, Divon M.  Glycemic control in gestational diabetes mellitus - how tight is tight enough:  small for gestational age versus large for gestational age?  Am J Obstet Gynecol 1989;161:646-653.

Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
PubMed ID: 2782347
Study Design:
Case Control
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To investigate the association between different levels of glycemic control and neonatal weight size (large for gestational age vs small for gestational age) infants, as well as the relationship between neonatal weight and selected maternal characteristics.

Inclusion Criteria:

Diagnosis of diabetes or normal using the National Diabetes Data Group Criteria or normal controls with oral glucose tolerance test in the 3rd trimester.

Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:


Study conducted between 1985-88.  Recruitment methods not described.

Design:  Case-Control Study

Blinding Used (if applicable):  not applicable

Intervention (if applicable):

  • Instructed in use of a memory-based reflectance meter.
  • Instructed to test blood glucose 7 times/day
  • Weekly or biweekly clinic visit
  • Diet alone or diet + insulin based on fasting plasma and mean blood glucose levels.
  • Counseled by nutritionist in diet management (3 meals + 1 snack), calories based on BMI:  BMI > 27: 25 kcal/kg, BMI <27: 30 kcal/kg
  • Insulin initiated when fasting or mean plasma glucose >95 mg/dl
  • Goals for blood glucose:
  •        Fasting: 60-80 mg/dl
  •        Preprandial, bedtime: 70-90 mg/dl
  •        Postprandial: <120 mg/dl
  •        Overall mean: <95 mg/dl

Statistical Analysis

Data analyses included univariate and bivariate statistical techniques with parametric and nonparametric tests.  Categoric data were analyzed with the chi-square and Fisher's exact tests.  Continuous data were analyzed by Student t test.  ANOVA was used to test for differences between the 3 groups.

Data Collection Summary:

Timing of Measurements

Weekly or biweekly clinic visits.

Dependent Variables

  • Neonatal size at birth

Independent Variables

  • Instructed in use of a memory-based reflectance meter.
  • Instructed to test blood glucose 7 times/day
  • Diet alone or diet + insulin based on fasting plasma and mean blood glucose levels.
  • Counseled by nutritionist in diet management (3 meals + 1 snack), calories based on BMI:  BMI > 27: 25 kcal/kg, BMI <27: 30 kcal/kg
  • Insulin initiated when fasting or mean plasma glucose >95 mg/dl

Control Variables

  • Obesity
  • Race
  • Parity
  • Gestational age at delivery
Description of Actual Data Sample:

Initial N:  334 women with gestational diabetes and 334 nondiabetic women

Attrition (final N):  334 cases, 334 controls

Age:  mean age cases:  31 +/- 5 years, mean age controls:  27 +/- 6 years

Ethnicity:  Cases:  39% White, 38% Black, 29% Hispanic; Controls:  35% White, 37% Black, 28% Hispanic

Other relevant demographics:

Anthropometrics:  Controls matched for control of obesity, race, parity and gestational age at delivery.

Location:  United States

Summary of Results:

Other Findings

Subjects were grouped according to mean blood glucose throughout pregnancy:

  • Low: < 86 mg/dl
  • Mid: 87 to 104 mg/dl
  • High > 105 mg/dl

The low blood glucose group had a significantly increased incidence of SGA infants (20%).

RR for having a SGA infant in the low glucose group (mean 81+6 mg/dl) was 2.56 (95% CI, 1.24 to 5.29) in comparison with other groups.

RR of having a LGA infant in the high glucose group was 20.92 (95% CI, 2.73 to 160.42).

The incidence of LGA infants was 21 fold higher in the mid blood glucose group than in the low blood glucose group (24% vs 1.4%, P<0.0001).

A significantly higher incidence of SGA infants (20% vs. 11%, P<0.001) was found between the low glucose group and the control group.

Author Conclusion:

Our data suggest that a relationship exists between level of glycemic control and neonatal weight.

Targeting the level of glycemic control to a range of 87 to 104 mg/dl (mean, 95+5 mg/dl) will result in neonatal size comparable to the general population.

Funding Source:
Milies Laboratory
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:

Tightly controlled study.  Too low blood glucose can increase risk for SGA infants and too high blood glucose can increase risk for LGA infants.

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? 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? 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? Yes
  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? 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? 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? 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? 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