GDM: Medical Nutrition Therapy (2016)


Maher N, McAuliffe F, Foley M. The benefit of early treatment without rescreening in women with a history of gestational diabetes. J Matern Fetal Neonatal Med. 2013 Feb; 26 (3): 318-320. doi: 10.3109/14767058.2012.733772. Epub 2012 Oct 18. PMID: 23039851.

Study Design:
Prospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To determine if women with a history of gestational diabetes mellitus who received treatment for GDM at their first pre-natal visit of a subsequent pregnancy would have a reduced risk of macrosomia in their infants.
Inclusion Criteria:
Pregnant women with a history of gestational diabetes mellitus who required insulin in their subsequent pregnancy.
Exclusion Criteria:
Women with a history of gestational diabetes mellitus who did not require insulin in their subsequent pregnancy.
Description of Study Protocol:


All women with previous history of GDM who attended the multi-disciplinary clinic from 2003 to 2010 were eligible. 


  • Retrospective chart review of all pregnant women with GDM followed at the National Maternity Hospital Dublin Ireland
  • Women with GDM who required insulin in their subsequent pregnancy were the cohort group. This group was started on a low glycemic index diet and insulin treatment as required at the first clinic visit rather than after screening for GDM. Timing of gestation treatment, birth weights, mode of delivery and neonatal complications were compared in this group's index pregnancy and subsequent pregnancy. 

Low glycemic index diet and insulin treatment started at the first clinic visit rather than after screening for GDM.

Statistical Analysis

Fisher's Exact test to compare the incidence of macrosomia in the index and subsequent pregnancy.

Data Collection Summary:

Timing of Measurements

Prenatal visits and post-delivery.

Dependent Variables

  • Maternal outcomes (vaginal vs. C-section rate, gestation week requiring insulin)
  • Neonatal outcomes (rate of macrosomia, NICU admission rate, birth weight higher than 4.0kg, RDS rate, neonatal hypoglycemia rate).

Independent Variables

Initiation of treatment earlier in pregnancy rather than after screening for GDM.

Control Variables

Women with a previous history of GDM.

Description of Actual Data Sample:
  • Initial N: N=95 
  • Attrition (final N): N=95
  • Age: Mean age 27.1 years  index pregnancy, 33.9 years subsequent pregnancy
  • Location: Dublin, Ireland.


Summary of Results:

Key Findings

There were no significant differences in delivery type (vaginal vs. Caesarean section) or rates of NICU admissions,  neonatal hypoglycemia or respiratory distress syndrome between the index and subsequent pregnancies. 

Variables Index Pregnancy Subsequent Pregnancy P-value
Gestation week starting treatment (diet or insulin) 31.2 week 10.2 week  
Gestation week starting insulin (mean) 29.2 19.1  
Incidence of macrosomia (percentage) 34.7 25.2 0.205
Incidence of macrosomia in those women requiring insulin in both pregnancies (percentage) 43.07 23.07 0.0204
Birth weight more than 4.0kg in women requiring insulin in both pregnancies (percentage) 36.9 16.9 0.0169


Author Conclusion:
  • The incidence of macrosomia was significantly less in the subsequent pregnancy in the group of women who required insulin in both pregnancies with early treatment of a low glycemic index diet and insulin as needed
  • Early treatment is beneficial to this high-risk group in the reduction of macrosomia.
Funding Source:
University/Hospital: University College Dublin
Reviewer Comments:
  • Did not define low glycemic index diet or measure dietary compliance
  • Did not discuss other variables such as maternal smoking, drug or alcohol use
  • Did not stratify for maternal BMI
  • Overweight or obese group may have had larger 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? 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? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? ???
  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? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? No
  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.) ???
  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%.) N/A
  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? Yes
  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? No
  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? 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? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  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? 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? No
  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)? 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes