GDM: Pharmacologic Therapy (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
The purpose of this study was to examine the outcome of the pregnancy and neonatal period in 1) women with gestational diabetes mellitus (GDM) and non-diabetic pregnant women and 2) in women with early and late diagnosis of gestational diabetes mellitus.
Inclusion Criteria:
  • Singleton pregnancy women with GMD and a control group of women at risk for GDM with a normal oral glucose tolerance test (OGTT) followed at the Department of Obstetrics and Gynecology, Glostrup University Hospital, Glostrup Denmark
  • Delivery of a liveborn baby or a stillborn baby with a gestational age > 28 weeks
Exclusion Criteria:
Excluded if not included above.
Description of Study Protocol:

Recruitment Subects were recruited from the Department of Obstetrics and Gynecology, Glostrup University Hospital, Glostrup Denmark from February 1996 to November 2000

Design Subjects were diagnosed with GDM based on 2 hour OGTT. This was done with a screening of family history of DM (first degree relative), body mass index (BMI) > 27 kg/m2, glucosuria, previous delivery of a baby with a birthweight >  4500 grams, previous GDM and age > 37 years. Women with GDM were treated with home monitoring of blood glucose and a low calorie diet, depending on BMI. Therapeutic aims were blood glucose before meals of < 6.0 mmol/l and 1.5 hour postprandial at <  8.0 mmol/l. When mean blood glucose > 6.5 mmol/l additional insulin was given. Women with a non-diabetic OGTT received standard obstetric care and no special action was taken of their OGTT result. Subjects in both groups were followed through out their labor, delivery and post partum and neonatal periods.

Blinding used (if applicable):  Not applicable

Intervention (if applicable):  Not applicable

Statistical Analysis

Categorical data were analyzed with Fisher's exact test, while continuous data were analyzed with Student's t test. Multivariate logistic regression analysis was used when appropriate. A p < 0.05 (two-sided) or 95% confidence interval (95% CI) below or above 1.0 was considered statistically signficant. In univariate analyses the p values were corrected for multiple comparisions by multiplying the observed p values with the number of tests (the Bonferroni method).

Data Collection Summary:

Timing of Measurements

Maternal data was collected through out the prenatal period, labor and delivery and post partum. Neonatal data was collected at delivery, and at 2 and 6 hours after delivery.

Dependent Variables

  • Maternal characteristics 
  • Neonatal outcomes 

Independent Variables

  • Effect of GDM on maternal characteristics and neonatal outcomes

Control Variables

  • None
Description of Actual Data Sample:

Initial N: 327 singleton pregnancies with GDM, 295 non-diabetic control

Attrition (final N): as above

Age: See table in results

Ethnicity: See table in results

Other relevant demographics: See table in results

Anthropometrics:  See table in results

Location: Glostrup Denmark

 

Summary of Results:

 

Maternal characteristics

Maternal Data

GDM

Control

P value

Age years mean +  SD 31.9 +  5.7 29.8  + 5.3 <0.05

Caucasian (%)

 255/326 (78)

 273/295 (36)

 <0.05

Pre-pregnancy BMI mean +   SD

 28.4 +  5.8

 26.6+   4.9

 <0.05

Glycosuria (%) 57/325 (18) 9/294 (3) <0.05
Previous GDM (%) 48/327 (15) 0/295 (0) <0.05

 

Pregnancy and delivery data
Pregnancy and delivery data GDM Control P Value
Induction of labor (%) 144/325 (44) 35/293 (12)  <0.05
 Gestational weeks at delivery (total)  39.1 +  1.7  39.8  + 2.0  < 0.05
 Gestational weeks at delivery (spontaneous onset)  38.8  + 2.0  40.0 +  1.6  < 0.05

Neonatal data
Neonatal data GDM Control p Value
Birth weight > 4500 g (%) 25/327 (8)  7/295 (2) 0.07
Admission to NICU 57/314 (18) 26/290 (9) <0.05

Other findings

Non-caucasian ethnicity, a family history of DM, BMI > 27, glucosuria, previous delivery of a baby > 4500 g, and age  37 were independently associated with GDM.

GDM and previous delivery of a large baby were independently associated with macrosomia.

Women who were dignosed early in pregnancy had a greater need for insulin treatment than women diagnosed late {18/50 (36%) vs. 24/277 (9%), p<0.05} and they were treated for a longer period (15 weeks vs. 8 weeks p<0.05).

Follow-up with OGTT from 2 months until 3 years postpartum showed DM in 19 of those with an early diagnosis of GDM vs. 15 of those with late diagnosis (p<0.05).

 

 
Author Conclusion:
Gestational diabetes mellitus was associated with a significantly lower gestational age at delivery and an increased rate of admission to the neonatal ward. Women diagnosed with GDM before 20 weeks of gestation had an increased need for insulin treatment during pregnancy and a high risk of subsequent DM compared with women diagnosed with GDM later in pregnancy.
Funding Source:
Reviewer Comments:

Incomplete data from all subjects -  no explanation of incomplete data. No definition of criteria for admitting neonate to NICU (? potential bias due to infant of a GDM mother), no measure of compliance of blood glucose testing or HbgA1c to determine glycemic control.

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? No
  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.) 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? ???
  4.1. Were follow-up methods described and the same for all groups? ???
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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.) ???
  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? ???
  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? 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? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  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? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  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)? Yes
  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