GDM: Medical Nutrition Therapy (2016)


Korpi-Hyövälti EA, Laaksonen DE, Schwab US, Vanhapiha TH, Vihla KR, Heinonen ST, Niskanen LK. Feasibility of a lifestyle intervention in early pregnancy to prevent deterioration of glucose tolerance. BMC Public Health, 2011, 11: 179

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 aim of the study was to evaluate if a lifestyle intervention since early pregnancy is feasible in improving the glucose tolerance of women at a high-risk for GDM in Finland.
Inclusion Criteria:
Pregnant women at eight to 12 weeks gestation were given a two-hour OGTT: They were included if they had one or more the following risk factors for GDM:
  • BMI over 25kg/m2, previous history of GDM or birth of child over 4.5kg; aged over 40 years, family history of diabetes (parents, children, siblings or grandparents)
  • The venous plasma glucose concentration after 12 hours' fasting in the morning was 4.8mmol to 5.5mmol per L and two-hour OGTT plasma glucose over 7.8mmol per L.
Exclusion Criteria:
Pregnant women at eight to 12 weeks gestation with no history of GDM or venous plasma glucose after 12 hours fasting in the morning under 4.8mmol or over 5.5mmol per L and two-hour OGTT plasma glucose over 7.8mmol per L.
Description of Study Protocol:
  • Recruitment: Women were recruited from two rural municipalities (Kahua-joki and Lapua, Finland) who attended maternal health care units during gestational Weeks Eight through 12
  • Design: High-risk women were randomized to lifestyle intervention or close-follow up group by the study physician using a computerized randomization list
  • Blinding used: Health care nurses who scheduled the study visits did not have access to the randomization list. Obsetricians who were not study physicans made decisions concerning the beginning of insulin treatment.


Statistical Analysis

Statistical analyses were based on the intention to treat Differences between the groups were analysed by Student’s T-test for continuous variables and the chi-square test and Fisher’s exact test for categorical variables. Statistical significance was set at the 95% level (P<0.05).

Close Follow-Up Group

The women were informed of the results of the OGTT during gestational weeks eight through 12 All women were also given general information on diet and physical activity to decrease the risk of GDM during pregnancy Dietary information was collected three times during pregnancy. They returned a self-reported exercise history and a monthly questionnaire of physical activity. The women were followed-up in the prenatal clinic of the municipal health center at one-month intervals, according to standard care in Finland.


Lifestyle Intervention Group

Dietary goals 
  • Energy recommendations: 30kcal for normal weight and 25kcal per kg of body weight per day for overweight women
  • Carbohydrate: 50-55% of energy
  • Fiber: 15g per 1,000kcal
  • Fat: 30% of energy; saturated fat, less than 10% of energy
  • Protein: 15-20% of energy
  • Women were encouraged to eat a diet rich in vegetables, berries and fruits, and to use low-fat dairy products, low-fat meat, soft margarines and vegetable oils, and whole grain products
  • The nutritionist gave dietary advice tailored to each subject individually six times. The three-factor eating questionnaire was used in the beginning of pregnancy and at weeks 36 through 40. 
  • The nurse in the health care centers had on average 13 appointments with the intervention women. The intervention women had no instruction on self glucose monitoring before GDM was diagnosed.
Physical activity
  • Moderate-intensity physical exercise during pregnancy was recommended. The formula (220 - age) × 0.65-0.75 was used to estimate the heart rate goals for moderate intensity exercise. Other measures of exercise intensity included the “talk test" i.e., exercise at an intensity in which the woman is able to maintain a conversation during exercise. A target rating of 12 to 14 on Borg’s scale of perceived exertion was also used. The pregnant women had six appointments with the physiotherapist. During sessions, the physiotherapist motivated the women individually to continue exercising during pregnancy or to start exercising and also gave written instructions for exercise and self care.
  • Previously sedentary women were instructed to begin with 15 minutes of continuous exercise three times per week, increasing gradually to 30-minute sessions four times per week. The goal of the exercise intervention was 30 minutes of daily physical activity if the woman previously exercised less than 2.5 hours per week and 45 minutes of activity if the woman already engaged in 2.5 hours or more per week of physical activity.
  • Recommendable types of exercise were brisk walking, Nordic walking, swimming, cycling and cross-country skiing. If the BMI of a woman was over 30kg/m2 and the woman was not physically active before pregnancy, the exercise was started with 15 minutes per day three times per week. Women were offered both aerobics classes and aquafit classes weekly.
Data Collection Summary:

Timing of Measurements

  • Two-hour OGTT was repeated during gestational weeks 26 to 28
  • Four-day food records were collected at baseline, weeks 26 to 28 and at the end of pregnancy
  • Three-factor eating questionnaire was completed twice
  • Monthly exercise reporting diaries were collected six times.

Dependent Variables

  • Diagnosis of GDM (according to the World Health Organization), fasting plasma glucose 5.6mmol per L or two hours plasma glucose 7.8mmol per L
  • Maternal outcomes (weight gain during pregnancy, pre-eclampsia, induction of labor, lacerations, Cesarean deliveries)
  • Neonatal outcomes (mean birth weight, macrosomia, gestational age, admissions to the neonatal intensive care unit, jaundice requiring phototherapy or respiratory distress).

Independent Variables

Lifestyle intervention (dietary counseling and physical acitivity).

Control Variables

Weeks of gestation at baseline.

Description of Actual Data Sample:
  • Initial N: 60
  • Attrition (final N): 54 (27 in Lifestyle Group, 27 in Close Follow-Up Group)
  • Age: 29.1 years in Lifestyle Group, 29.8 years in Close Follow-Up Group
  • Ethnicity: N/A.
Other Relevant Demographics
  • Anthropometrics 
    • BMI
      • Lifestyle group: 27.3±6.0
      • Close Follow-Up Group: 25.5±3.4 (NS).
    • BMI over 25kg/m2
      • Lifestyle Group: 18 (60%)
      • Close Follow-Up Group: 17 (56.7%; NS).
  • Location: Finland.
Summary of Results:
  • There were no significant differences between groups in total weight gain, weight gain at the end of pregnancy, fasting glucose, OGTT one-hour glucose, two-hour glucose or the area under the curve. Neither group had any individuals who required insulin therapy.
  • Gestational diabetes incidence was three (11.1%) in the Lifestyle Intervention Group and one (3.7%) in the Close Follow-Up Group (NS)
  • The Intervention Group had a lower weight gain during pregnancy: 11.4±6.0kg vs. 13.9±5.1kg (P=0.062), adjusted by the prepregnancy weight
  • The mean birth weight was greater, 3,871±567g in the Lifestyle Intervention Group (P=0.047, adjusted by the prepregnancy weight of the women), compared with the Close Follow-Up Group: 3,491±573g.
Author Conclusion:
  • Early intervention with an OGTT and simple lifestyle advice is feasible
  • A more intensive lifestyle intervention did not offer additional benefits with respect to glucose tolerance, although it tended to ameliorate the weight gain.
Funding Source:
University/Hospital: Seinajoki central hospital, Kuopio University Hospital, University of Eastern Finland
Reviewer Comments:
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? ???
  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? ???
  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.) N/A
  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? Yes
  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? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  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? 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? 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? ???
  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? ???
  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)? ???
  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? No
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