GDM: Carbohydrate (2016)
- Women screened via oral glucose tolerance test between 24th and 28th weeks of gestation
- Gestational diabetes or gestational mild hyperglycemia diagnosis
Not explicitly stated, but participants were excluded for the following reasons:
- Treated hypertension
- Asthma
Recruitment
1 out of every 4 women participating in a wider prospective study conducted from Jan 1993 to December 1993 in 15 maternity hospitals in northern France were selected to be a part of the nutrition survey.
Design: Longitudinal Study
Blinding used (if applicable): not applicable
Intervention (if applicable)
This study was ancillary to the following larger study:
- Intervention for parent study was intensive monitoring by a dietitian and endocrinologist. Patients were seen weekly during the first month then every 2 weeks until delivery.
- At each visit, fasting and 2-hr postporandial serum glucose, dietary adherence , weight changes, and blood pressure were evaluated. Self monitoring included urine analysis for ketones 3 times/day and blood glucose 4 times/day.
- Energy content of prescribed diet was based on prepregnancy BMI< prediagnostic weight gain, and energy intake evaluated by 3-month diet history. Prescription >=1800kcal/day
- 50-55% carbohydrate, 30-35% fat, 10-15%protein
- Insulin prescribed as needed
Statistical Analysis
- Univariate analyses using nonparametric tests - Spearman correlations, Wilcoxon
- Forward stepwise regression analyses - effect of maternal age, smoking, parity, prepregnancy BMI, pregnancy weight gain, infant sex, gestational duration, insulin therapy, fasting and 2-hour postprandial serum glucose, and energy and macronutrient intake on infant birthweight
Timing of Measurements
- Screening between 24-34 weeks of gestation
- Patients seen weekly for the first month and bi-weekly thereafter until delivery
Dependent Variables
- Birthweight
- Compared to growth curves for the French populations (AUDIPOG study):
-large-for gestational-age (LGA) when birthweight > 90th percentile
- small-for-gestational-age (SGA) birthweight < 10 th percentile
Independent Variables
- Baseline Diet - first interview used 3-month diet history adapted from Burke
- Diet during intervention period - Mean of two 3-day food records (2 weekdays and 1 weekend day) during the 3rd and 7th weeks of follow-up. Data were checked by a dietitan in each study center, and nutrient intake was calcualted using a Frendch food composition table after coding by two trained dietitians
Control Variables
- Maternal age
- Smoking
- Gestational age - last menstrual period and early ultrasonographic assessment
- Prepregnancy BMI - self-report measured at the first exam
- Mean fasting serum glucose/2-hr postprandial glucose-average of all values determined at each visit during treatment
- Parity
- Pregnancy weight gain
- Infant sex
- Gestational duration
- Insulin therapy
Initial N: 99
Attrition (final N): 80
- 1 premature birth
- 18 diet underreporters, defined as reported Energy intake/basal metabolic rate (BMR) ratio <1.14 : BMR estimated using Schofield's equations using age, sex, and weight
Age: 30.2±5.3 (mean±sd) years
Ethnicity: French, not further specified
Other relevant demographics:
- 66% multiparous
- 16% smoked during pregnancy
Anthropometrics Prepregnancy BMI: 25.2±5.2 (mean±sd)
Location: 15 maternity hospitals in northern France
Variables |
Standardized regression coefficient (n=73) R^2=0.27 |
p value |
Gestational duration, wk |
0.34 |
0.002 |
Smoking |
-0.27 |
.01 |
Carbohydrate, g/d |
-0.24 |
0.03 |
Other Findings
- 61% GDM; 39% mild hyperglycemia
- Birthweight: 3402±438 (mean±sd) kg; 16% LGA, 4% SGA
- 39% babies female
- Gestation duration: 39.3±1.2 (mean±sd)
- 24% (n=19) had a carbohydrate had carbohydrate intake lower than the prescribed level by at least 20%
Government: | Conseil Regional Nord CPAM | ||||
Industry: |
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- Eligibility criteria not explicitly stated
- Unclear how the "1 in 4" participants selected from parent study; results said participants in sub-study were of higher SES compared to overall sample
- Effect measures inadequate: Since diet was measured as part of an intervention to encourage 50-55% kcal from carbohydrate, better compliers with overall intervention may have had higher carbohydrate intake, thereby results of study could be due to factors other than higher carbohydrate diet
- Carbohydrate has smaller effect than smoking; are smaller babies healthier babies? Goal is to prevent macrosomia, not encourage low birth weight
- Could have presented results with and without "underreporters" as macronutrient composition may have been accurately reported
- Limitations not described adequately: i.e. measurement error of diet, uncertainty regarding whether finding was due to better compliance to other intervention factors or adherence to dietary recommendations; Statement that "careful distribution of carbohydrates and use of low glycemic index foods helping in limiting postprandial hyperglycemia" was not tested in this intervention
- Study supported by many industry groups, including Novo Nordisk, lily, Nestle, Roche, Schering
Quality Criteria Checklist: Primary Research
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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? | ??? | |
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? | No | |
3. | Were study groups comparable? | N/A | |
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? | 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? | 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")? | 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? | N/A | |
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.) | N/A | |
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? | 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? | No | |
7.1. | Were primary and secondary endpoints described and relevant to the question? | No | |
7.2. | Were nutrition measures appropriate to question and outcomes of concern? | No | |
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? | N/A | |
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)? | 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? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | No | |
9.1. | Is there a discussion of findings? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | No | |
10. | Is bias due to study's funding or sponsorship unlikely? | ??? | |
10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
10.2. | Was the study free from apparent conflict of interest? | ??? | |