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GDM: Postpartum Care (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To examine whether lactation was associated with differences in glucose tolerance, insulin sensitivity and secretion, body habits, and adipose tissue in a population of women with a history of GDM.
Inclusion Criteria:
  • Breast feeding and nonbreastfeeding women with a history of gestational diabetes
  • Vaginal delivery of a live singleton infant after 36 weeks of gestation
  • Completion of informed consent
Exclusion Criteria:
Exclusion criteria was not delineated.
Description of Study Protocol:

Recruitment : Recruitment from physician offices and offered participation.

Design : Matched population

Blinding used (if applicable):  not applicable

Intervention (if applicable)

All women were advised to exercise 3 times a week for 1/2 hour and also to achieve their ideal body weight within 12 months postpartum.

Statistical Analysis: 

  • Population means were compared by 2-sample t tests, as well as Wilcoxon ranked sum test
  • Correlations were sought between insulin sensitivity parameters and adipose tissue measures, waist-hip ratios, body mass index, and lipid values
  • Repeated measures analysis of variance were used to evaluate results for lactating and non lactating women
  • Categorical variables were compared by Fisher's exact test.

 

Data Collection Summary:

Timing of Measurements

At 3 months postpartum, participants came to the Clinical Investigation Unit on 2 separate occasions, having fasted after midnight.

The following was documented at first visit:

  • heart rate and blood pressure after sitting quietly for 10 minutes.
  • weight gain of pregnancy
  • infant birthweight,
  • smoking history,
  • hours of weekly exercise
  • weight, height, waist-hip ratios

Three months postpartum was chosen for evaluation in an effort to minimize the potential variability of frequency and duration of lactation that would ensue as infant diets were supplemented by bottle feeding and solid foods.

  1. Oral glucose tolerance test(OGTT)-each woman completed an oral glucose tolerance test after 3 days of ad libitum carbohydrate intake.Women in the lactating group were instructed to breastfeed their infant within 2 hours before the OGTT.
  2. Cholesterol,triglycerides, and glucose-baseline samples were taken,75g of oral glucose over 10 minutes,and a second blood sample for glucose was drawn at 120 minutes.
  3. Frequently-sampled intravenous glucose tolerance test(FSIGT)-within 2 weeks of the OGTT,each participant went to the Clinical Investigation Area after a 12-hour fast for FSIGT.Women in the lactating group were asked to have breastfed their infant within 2 hours before the onset of testing.This testing was performed in the first 2 weeks after a menstral cycle if the woman had already experiences the return of her menses.

      4. Glucose,insulin,and C-peptide sampling(see Table 1)

                                Table 1 Schedule of Intravenous Glucose Tolerance Test

Sample

Timing
the 4 baseline samples of blood -15,-10,-5 and -1 minutes
Bolus of 50% dextrose  was then administered over 1 minute at a dose of 300 mg/kg. Subsequent blood samples were drawn at 2,3,4,6,8,10,12,14,16,and 19 mintes after the glucose bolus.
Bolus injection of regular insulin (starting at 20 minutes) at a dose of 0.03 U/kg was given over 1 minute. Blood samples were again taken at 22,23,24,25,27,30,40,50,60,70,80,100,120,140,160, and 180 minutes

                                                                                                          

  Dependent Variables

  • Fasting glucose -impaired glucose tolerance and diabetes were diagnosed by American Diabetes Association. Plasma glucose concentrations were determined by glucose oxidase method (Synchron CX Beckman Delta System:Beckman,Irvine,CA). Precision of glucose assay 2.0% within and 3% between assays at a mean of 5.6 mmol/L.
  • Fasting insulin -serum insulin levels were assayed on the Abbott IMx Analyzer(Abbott Labs, Chicago,Il) by microparticle enzyme immunoassay technology. Persion of insulin was 4% within and 4.7% between assays at a mean of 14.5 mU/L. Insulin rather than tolbutamide modification of the FSIGT was chosen, as it was expected some of the women would have already developed diabetes and therefore have had too small an insulin response to tolbutamide to allow mathematical modeling of the results.
  • Cholesterol
  • Triglycerides
  •   S1(x10-4 min-1/(µ U/mL)
  • SG(x102 min1)
  • AIRg(µ U/mL) -The FSIGT data was analyzed by Bergman's Minimal Model Method to provide stimates of insulin sensitivity and glucose effectiveness. First phase insulin response to glucose was determined from the FSIGT as the mean insulin from 2 to 10 minutes minus basal insulin.
  • DI (x10-4 min-1) -the disposition was calculated as the product of S1 x AIRg
  • Viseral fat
  • Subcutaneous fat
  • Viseral/subcutaneous fat

Independent Variables

  • age
  • weight gain during pregnancy
  • peak pregnancy weight
  • weight loss by 3 months
  • weight
  • BMI
  • W/H ratio
  • Systolic blood pressure
  • Diastolic blood pressure
  • Infant weight
  • Exercise(h/wk)
  • Duration of GDM(wk)
  • Smoking
  • on insulin during pregnancy
  • IGT at 3 months
  • Diabetic at 3 months
  • On Oral Contraceptives at 3 months

Control Variables-not applicable

 

Description of Actual Data Sample:

Initial N: 26 women; 14 who had breastfed for at least 3 months and 12 who had not breastfed past hospital discharge.

Attrition (final N): 26

Age: Lactating women=30.9±1.3 years; Nonlactating women=30.7±1.3 years

Ethnicity: Caucasian, consistent with local population demographics.

Other relevant demographics:

Anthropometrics:

Location: British Columbia ,Canada

 

Summary of Results:

Table 2. Population Demographics

 

Lactating Women

Nonlactating Women

P
No.

14

 12

  
Age(y)

30.9±1.3

 30.7±1.3

  .89
weight gain during pregnancy(kg)

11.6±1.6

 11.2±2.0

  .86
Peak Pregnancy weight(kg)

86.1±5.4

 92.9±7.9

  .47
Weight loss by 3 months

9.2±1.3

 10.3±2.8

  .69
Weight(kg)

76.8±18.5

 72.9±8.0

  .67
BMI

30.0±1.9

 30.7±2.1

  .81
W/H ratio

0.82±0.02

 0.81±0.02

  .73
Systolic blood pressure(mm-Hg)

114.3±1.8

 118.3±3.7

  .33
Diatolic blood pressure(mmHg)

71.8±71.8

 73.6±2.4

  .57
Infant weight(kg)

3.69±0.20

 3.68±2.0

  .97
Exercise(h/wk)

1.4±10.6

 2.3±0.8

  .35
Duration of GDM(wk)

13.2±1.6

 13.5±2.5

  .92
Smoking

2

 1

  1.00
On onsulin during pregnancy

2

 2

  1.00
IGT @ 3 months

4

 2

  .64
Diabetic @ 3 months

1

 3

  .59
On OC @ 3 months

3

 5

  .66

 NOTE: Results are reported as mean±SEM   Abbreviation: OC,oral contraceptive

Table 3. Insulin,Glucose, and Adipose Measures

  Lactating Women Nonlactating women

P
Fasting glucose(mmol/L)

5.3±0..3

 5.4±0.2

 .58
Fasting Insulin(pmol/L)

 94.2±15.6

 86.4±12.0

 .70
Cholesterol(mmol/L)

 5.0±0.4

 4.5±0.3

 .27
Triglycerides(mmol/L)

 1.3±0.2

 2.0±0.4

 .12
S1(x10-4min-1/(µ/mL)

 4.97±0.78

 3.44±1.00

 .24
SG(x10 2 min 1)

 1.92±0.22

 1.56±0.19

 .25
AIRg(µU/mL)

 31.9±9.9

 18.3±5.6

 .26
DI(x10-4 min-1 )

 129.9±26.0

 53.4±18.0

 .03
Viseral fat(cm2)

 103±14

 97±15

 .75
Subcutaneous fat(cm2)

 362±36

 460±68

 .19
Visceral/subcutaneous fat

 0.29±0.03

 0.25±0.05

  .43

NOTE. DI:AIRgxS1. Results are reported as mean±SEM.

Abbreviations: AIRg, accurate insulin response to glucose; S1,insulin sensitivity; SG, glucose effectiveness.

 

Author Conclusion:

The authors concluded that within a matched population of women with a history of GDM,  3 months of breast feeding was associated with improved pancreatic ß-cell function, but not with any significant differences in glucose tolerance, adipose tissue mass, or adipose distribution.

Study Limitation-3 months of lactation may have been insufficient time to result in significant body habit alterations.

Funding Source:
Reviewer Comments:
Matched population is a type of repeated measures design where the repeated measurement is not of the same subjects but of very similar subjects matched to have like key attributes. 
This design controls only for matched attributes.
 
A limitation of this design is the assumption that the researcher actually knows what extraneous factors that need to be controlled for, i.e. matched - and in some circumstances this may not always be the case.
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) ???
 
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) ???
  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? 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.) No
  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? 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? 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? 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)? 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? 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? ???
  10.1. Were sources of funding and investigators' affiliations described? ???
  10.2. Was the study free from apparent conflict of interest? ???