GDM: Medical Nutrition Therapy (2016)


Koivusalo SB, Rönö K, Klemetti MM, Roine RP, Lindström J, Erkkola M, Kaaja RJ, Pöyhönen-Alho M, Tiitinen A, Huvinen E, Andersson S, Laivuori H, Valkama A, Meinilä J, Kautiainen H, Eriksson JG, Stach-Lempinen B. Gestational Diabetes Mellitus Can Be Prevented by Lifestyle Intervention: The Finnish Gestational Diabetes Prevention Study (RADIEL): A Randomized Controlled Trial. Diabetes Care. 2015 Jul 29. pii: dc150511. [Epub ahead of print] PMID: 26223239

PubMed ID: 26223239
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The primary outcome of the Finnish Gestational Diabetes Prevention Study (RADIEL) was to examine the effect of combined moderate physical activity and diet intervention in high-risk women on the incidence of GDM in a randomized controlled study setting.
Inclusion Criteria:
Eligible participants for the study were women aged 18 years or older, pregnant at less than 20 weeks of gestation, with a history of GDM or a pre-pregnancy BMI of at least 30kg/m2.
Exclusion Criteria:
  • Type 1 or type 2 diabetes or GDM diagnosed before 20 weeks of gestation
  • Use of medication that influences glucose metabolism, such as continuous therapy with oral corticosteroids or metformin
  • Multiple pregnancy
  • Physical disability
  • Current substance abuse
  • Severe psychiatric disorder
  • Significant difficulty in cooperating (e.g., inadequate Finnish language skills).
Description of Study Protocol:


  • Participants were recruited from obese women, primarily in association with the first trimester screening ultrasound and women with prior GDM, by personal invitation letters sent out based on data in the hospital registry
  • In addition, notices in newspapers, social media and antenatal clinics were used.


  • Randomization was done by permuted blocks stratified by risk factors (BMI at least 30kg/m2, history of GDM)
  • The randomization was performed by a study nurse and by dispensing the next sequentially numbered subject code and opening the corresponding code envelope, which included the intervention arm to be assigned to the subject.

Blinding Used
Study physicians were blinded to study groups when evaluating maternal and neonatal diagnoses.


Study participants received lifestyle counseling from study nurses and dietitians who were specifically trained for their tasks. The participants visited the study nurse three times during pregnancy. These visits were structured, but the counseling was individualized according to the stage of the pregnancy. At the time of study enrollment, the participants attended one two-hour group counseling session led by a dietitian.
  • The study visits took place at the following times:
    • Baseline visit was at 13.3 weeks of gestation [interquartile range (IQR), 12.0 weeks to 14.6 weeks of gestation]
    • Second visit at 23.1 weeks of gestation (IQR, 22.4 to 24.1 weeks of gestation)
    • Third visit at 35.1 weeks of gestation (IQR, 34.4 to 35.6 weeks of gestation).
In addition, the participants visited antenatal clinics according to standard national practice. For women with a pre-pregnancy BMI of at least 30kg/m2, the recommendation was no weight gain during the first two trimesters. The dietary advice was based on contemporary Nordic Nutrition Recommendations (2004). The dietary counseling focused on optimizing participants’ consumption of vegetables, fruits and berries, whole-grain products rich in fiber, low-fat dairy products, vegetable fats high in unsaturated fatty acids, fish and low-fat meat products, and a lower intake of sugar-rich foods. A food frequency questionnaire designed for this study was filled in before each visit to the study nurse.

To measure the general adherence to the recommended diet, a dietary index was developed based on the food frequency questionnaire, with higher scores indicating better diet quality. The dietary index includes 11 components that represent each topic of the counseling and were scored based on reported intake frequency, as follows:

  • Snacks (0–2 points)
  • Sugar-sweetened beverages (0–1 point)
  • Vegetables (0–2 points)
  • Fruits and berries (0–1 point)
  • Low-fat cheese (0–1 point)
  • Cooking fat (0–1 point)
  • Spread fat (0–2 points)
  • Fast food (0–1 point)
  • High-fiber bread and cereals (0–2 points)
  • Fish (0–2 points)
  • Low-fat milk (0–2 points).
The highest score (17 points) was set to reflect the highest adherence to the recommended intake of each score item. 

Regarding physical activity, the aim was to achieve a minimum of 150 minutes of moderate-intensity physical activity per week and to adopt an overall active lifestyle. The participants and the study nurses planned (and during the follow-up, they updated) an individual physical activity program. Participants had access, free of charge, to public swimming pools or guided exercise groups once a week, provided by the municipalities. Evaluation of leisure-time physical activity was based on the self-reported time spent weekly on physical activity that makes a participant at least slightly out of breath and sweaty. Pre-pregnancy physical activity was assessed at baseline in a similar way.

In the Control Group, participants received general information leaflets on diet and physical activity, usually provided by local antenatal clinics. Also, during pregnancy the Control Group participants visited the study nurse three times, to make measurements, obtain blood samples and to administer questionnaires, as well as antenatal clinics, according to standard practice.

Statistical Analysis

  • The comparison between groups was made by using a T-test, X2 test, or Mann-Whitney test
  • When using adjusted models, ANCOVA, a logistic regression model or a median regression (least absolute-value) model was applied
  • Repeated measures were analyzed using a generalized estimating equation (GEE) model with the unstructured correlation structure
  • GEEs were developed as an extension of the general linear model to analyze longitudinal and other correlated data
  • In the case of violation of the assumptions (e.g., non-normality), a bootstrap-type test was used (10,000 replications)
  • The normality of the variables was tested by using the Shapiro-Wilk W-test
  • All statistical analyses were performed unadjusted and adjusted for age, pre-pregnancy BMI, previous GDM status, weeks of gestation and baseline value.
Data Collection Summary:

Timing of Measurements
Participants underwent OGTT at study enrollment (20 weeks gestation) and at 24 to 28 weeks gestation.

Dependent Variables

  • GDM diagnosis: Decined as one or more pathological glucose values in a 75-gram, two-hour oral glucose tolerance test (OGTT; run by a central laboratory) with the following diagnostic thresholds:
    • Fasting plasma glucose at least 5.3mmol per L
    • One-hour value at least 10.0mmol per L
    • Two-hour value at least 8.6mmol per L.
  • Maternal outcomes: Pregnancy-induced hypertension, pre-eclampsia, Cesarean section
  • Neonatal outcomes: Birthweight over 4,500g, crown-heel length, gestational age at birth, respiratory distress.

Independent Variables

  • Individualized counseling on diet, physical activity and weight control from trained study nurses
  • One group meeting with a dietitan.

Control Variables

Description of Actual Data Sample:

Initial N

  • Intervention Group: 155
  • Control Group: 138.


  • Intervention Group: 144
  • Control Group: 125.


  • Intervention Group: 32.3 years
  • Control Group: 32.6 years (NS).

Caucasian Finnish women.

Other Relevant Demographics

  • Anthropometrics: No signficant differences between groups in body weight, gestational age at baseline, prior GDM percentage, smoking, dietary index or physical activity index at baseline
  • Location: Helsinki Finland and Lappeernata, Finland.
Summary of Results:

GDM Diagnosis

  • GDM was diagnosed in 20 participants [13.9% (95% CI, 8.7% to 20.6%)] in the Intervention Group and in 27 participants [21.6% (95% CI, 14.7% to 29.8%)] in the Control Group (P=0.097 unadjusted; P=0.044 after adjustment for age, pre-pregnancy BMI, previous GDM status and number of weeks of gestation at the time of the diagnostic OGTT). The crude relative risk for GDM was 0.64 (95% CI, 0.38 to 1.09) in the Intervention Group.
  • Women belonging to the Intervention Group had a crude reduction in fasting plasma glucose concentration of 20.18mmol per L (95% CI, 20.24mmol to 20.12mmol per L) from baseline to the third trimester, compared with 20.07mmol per L (95% CI, 20.13mmol to 20.02mmol per L) in the Control Group (P=0.026 unadjusted; P=0.011 after adjustment for age, pre-pregnancy BMI, previous GDM status, the number of weeks of gestation and baseline glucose concentration).
  • In the Intervention Group, the two-hour glucose value increased from baseline to second trimester by 0.54mmol per L (95% CI, 0.35mmol to 0.72mmol per L) and in the Control Group by 0.55mmol per L [(95% CI, 0.33mmol to 0.78mmol per L) P=0.92 unadjusted; P=0.42 after adjustment for age, pre-pregnancy BMI, previous GDM status, number of weeks of gestation and baseline glucose concentration].

Gestational Weight Gain
There was a difference in gestational weight gain between the Intervention Group [2.5kg (95% CI, 2.1 to 3.0]) and the control group [3.1 kg (95% CI, 2.7 to 3.5)] from baseline to the second trimester (at the time of the OGTT at Week 23.4, on average) and the mean difference was 20.5kg [(95% CI, 21.1 to 0.05) P=0.072 unadjusted; P=0.039 after adjustment for age, previous GDM status, the number of weeks of gestation, and baseline weight]. The gestational weight gain was 7.6kg (95% CI, 6.7kg to 8.3kg) in the Intervention Group and 7.7kg (95% CI, 7.1kg to 8.4kg) in the Control Group from baseline to the third trimester and the mean difference was 20.2kg [(95% CI, 21.1 to 0.8) P=0.74 unadjusted; P=0.37 after adjustment for age, previous GDM status, the number of weeks of gestation and baseline weight)].

Dietary Index Score
The dietary index score improved more among women in the Intervention Group [0.7 (95% CI, 0.3 to 1.1)], compared with those in the Control Group [0.3 (95% CI, 20.1 to 0.7)] and the mean difference was 0.4 [(95% CI, 20.1 to 1.0) P=0.16 unadjusted; P=0.037 after adjustment for age, pre-pregnancy BMI, previous GDM status, the number of weeks of gestation and baseline values).

Physical Activity
Women in the Intervention Group increased their median weekly leisure time physical activity by 15 minutes (95% CI, one to 29 minutes), while the physical activities of women in the Control Group remained unchanged (P=0.17 unadjusted; P=0.029 after adjustment for age, pre-pregnancy BMI, previous GDM status, number of weeks of gestation and baseline values).

Maternal and Neonatal Outcomes
There were no differences in the other maternal pregnancy or birth outcomes assessed between the Intervention and Control Groups.
Author Conclusion:
  • GDM can be prevented in a high-risk population by simple, easily applicable lifestyle interventions
  • Our findings suggest that individualized lifestyle intervention should be initiated in early pregnancy in high-risk women and continued throughout pregnancy
  • These results are unique and highly promising. Preventing GDM may have major short- and long-term health consequences for both the mother and the child.
Funding Source:
Government: The Finnish Foundation for Cardiovascular Disease, The Finish Diabetes Research Foundation, State Provincial Office of Southern Finland, Social Insurance Institution of Finland
Reviewer Comments:
Well thought out study, 
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? 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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
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? Yes
  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.) 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? 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? N/A
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  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? Yes
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? ???
  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)? 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? Yes
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