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GDM: Postpartum Care (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To identify ante-partum and early post-partum (one year) clinical and metabolic characteristics capable of predicting the future development of type 2 diabetes in pregnant women of Mediterranean area affected by gestational diabetes mellitus (GDM).
Inclusion Criteria:
  • GDM patients in the Department of Medical and Surgical Sciences, Chair of Metabolic Disease Padova University
  • GDM diagnosed according to Carpenter and Coustan's criteria after screening with the glucose challenge test patients between the 24 th and 28 th weeks of pregnancy; patients who were positive (i.e., plasma glucose 1 hour after GCT >= 140 mg/dl) were subjected to the oral glucose tolerance test (OGTT) with 100 gr. glucose. GDM was diagnosed if any two of the following values were reached or exceeded: fasting plasma glucose >= 95 mg/dl, 1h >= 180 mg/dl, 2h >= 155 mg/dl, 3h >= 140 mg/dl. Pregnant women presenting one or more GDM risk factors were screened earlier.
Exclusion Criteria:
  • Development of Type I diabetes after pregnancy
Description of Study Protocol:

Recruitment

Subjects were selected from a group of ~ 650 women screened for GDM in 1990-1992.

Design

Patient characteristics, diagnosis and severity of GDM, time and type of delivery, and fetal outcomes were recorded.  Additional predictors considered included body weight, BMI, OGTT with plasma glucose and insulin measurements (at 0, 30, 60 and 120 min), and fasting and post-prandial plasma glucose values one year after pregnancy. 

Blinding used (if applicable)

Medical records abstractors could have been blinded to diabetes diagnosis, but this was not mentioned.

Intervention (if applicable): not applicable

Statistical Analysis

Means ± SD and evaluated by Student's t-test. Variance analysis, the exact Fisher test and χ 2 analysis were used for categorical data. Differences were considered to be statistically significant at p < 0.05.

Data Collection Summary:

Timing of Measurements

Antenatum, 1 year post-pregnancy, follow-up screening for diabetes annually for 5 years post-partum.

Dependent Variables

  • Diabetes during annual follow-up for the first 5 years postpartum was diagnosed according to the World Health Organization criteria, using an OGTT with 75 gr. of glucose. They were advised to contact the diabetologist if any symptoms suggestive of diabetes developed (polydipsia, polyuria, polyphagy, loss of weight).

Independent Variables

  • Patients' age, family history of diabetes, pre-pregnancy body weight and BMI, previous GDM and obstetric outcome (parity, repeated abortion, macrosomia, stillbirths) were recorded.
  • Gestational age at the time of diagnosis of GDM, glucose levels of diagnostic OGTT, fasting, 1-h post-prandial plasma glucose and HbA 1c at the third trimester of pregnancy, weight gain and insulin therapy.
  • Time and type of delivery (abortion, caesarean section, spontaneous labour) and fetal outcome (weight, birth trauma, stillbirths) were analysed. Macrosomia was considered as in fant weight >= 4 kg; Large for Gestational Age (LGA) as a birth weight > 90th percentile, Small for Gestational Age (SGA) a birth weight < 10th percentile; the ponderal index was calculated as birth weight (g)/length (cm) 3 X 100.
  • Body weight, BMI, OGTT with plasma glucose and insulin measurements (at 0, 30, 60 and 120 min), and fasting and post-prandial plasma glucose values one year after pregnancy, were all taken into consideration.

Control Variables

Description of Actual Data Sample:

Initial N:70

Attrition (final N):  5 with type I diabetes excluded from the study (65)

Age: During pregnancy: Mean for normal glucose tolerance 32 +/- 5 years, 37 +/- 5 years for impaired glucose tolerance and 34 +/- 4 years for type 2 diabetes

Ethnicity: Mediterranean

Other relevant demographics: Mean BMI for normal glucose tolerance 24.8 +/- 5, 27 +/- 6 for impaired glucose tolerance and 29 +/- 5 for type 2 diabetes

Anthropometrics Those who developed impaired glucose tolerance were significantly older, and those who developed type 2 diabetes had a significantly higher BMI.

Location: Padova, Italy

Summary of Results:

 

Variables

Normal glucose tolerance

(n=49)

Impaired Glucose Tolerance

(n=6)

Type II diabetes

 (n=10)

Statistical Significance of Group Difference

GDM diagnosis, gestational week

28±8

28±10

21.5±7*

0.016

Weight gain

 

10.5±3.6

9.2±3.3

 

5.6±4.7*

 <0.003

Insulin therapy (during pregnancy)

 16.3%

 33.3%

60% *

 

 <0.003
Post-partum BMI

 

24±4

 

27±6

 

29.6±6*

 0.013
Post-partum fasting glucose

86±12

101±14*

 107±13 <0.027
Post-partum post-prandial glucose

98±19

112±9

112±23*

 <0.001

 

Other Findings

  • No differences were found in the three groups of patients as regards frequency of abortion, caesarean section or spontaneous delivery.
  • Neonatal outcome, mean weight and ponderal index, frequency of macrosomia, LGA and SGA, did not differ in the three groups. There were no cases of birth trauma or stillbirths in any group.
Author Conclusion:
On the basis of these results, early diagnosis of GDM, close obstetric and metabolic follow-up during pregnancy, and regular follow-up of GDM patients at greater risk of developing diabetes after pregnancy must be reinforced, if we are to prevent diabetes in these women.
Funding Source:
University/Hospital: Padova University
Reviewer Comments:

Selection of 70 patients from 600 unclear - in the discussion suggests it was first 70

Unclear if outcome status was known by those abstracting information on predictors

Used unpaired t-test but there were 3 groups. ANOVA or regression more appropriate; multivariate analysis would have provided more information about relative contribution of each of the factors in predicting disease

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) N/A
  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) N/A
 
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? No
  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? ???
  2.2. Were criteria applied equally to all study groups? ???
  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? 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? Yes
  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? Yes
  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? 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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  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? 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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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? 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? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  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)? No
  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