EAL

GDM: Weight Management (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the relationship between estimated caloric intake with maternal blood glucose profile and infant outcome in a group of Chinese women with gestational diabetes mellitus (GDM) treated by diet alone.

Inclusion Criteria:

Chinese women (speak Cantonese) with GDM 90-120% ideal body weight

prescribed caloric intake 30kcal/kg

no complications other than GDM

Exclusion Criteria:

pre-existing diabetes

underlying medical complications requiring dietary restriction or control

multiple pregnancies

Description of Study Protocol:

Recruitment Women recruited from hospital serving a population that is 95% ethnic Chinese at the time of their first blood glucose profile assessment following diet therapy

Design Women diagnosed with GDM were referred to a dietitian for diet advice and blood glucose profile (fasting and 2 hour after breakfast, lunch, and dinner) was performed 1 week after their initial dietary consultation. Women were recruited for the study at the time of their first blood glucose profile assessment following the beginning of diet therapy. Participants completed a diet survey form from the day prior to the third day following the blood glucose profile. All other data were collected from hospital records after delivery.

Blinding used (if applicable): Not applicable

Intervention (if applicable): Not applicable

Statistical Analysis Continuous variables by t-test and one way ANOVA with post-hoc analysis by Duncan's multiple range test set at the 5% level. Categorical variables by chi-squared test and Spearman's correlation coefficient. Used SPSS version 10.0.

Data Collection Summary:

Timing of Measurements

GDM diagnosis- 75g OGTT for all high risk (>34years old, family history, obesity, glycosuria) at first antenatal visit; all women have random plasma glucose at 28-30 weeks and if results abnormal, undergo OGTT. OGTT assessed using World Health Organization criteria
Blood glucose profile measured for this study was performed 1 week after their initial dietary consultation.
5-day diet record (including one weekend) was assessed the day before, day of, and 3 days after the blood glucose profile assessment.
All other data were collected from hospital records after delivery.

Dependent Variables

Blood glucose profile - fasting and 2 hour after breakfast, lunch, and dinner were collected from hospital records after delivery.
Pregnancy outcomes were collected from hospital records after delivery.

Independent Variables

Caloric intake - measured by 5-day diet survey form. Portion size aids using hand size were used. The survey forms were distributed and the food diary was started 1 week after seeing the dietitian. Total caloric intake was estimated using Nutrition IV together with a locally generated database for Chinese food. Subjects were categorized by their average daily intake into tertiles for analysis

Control Variables

Maternal height and weight

Description of Actual Data Sample:

Initial N: 85 of 88 women approached to participate were provided with the diet survey. 23 of 85 were excluded from the analysis, because 12 were not returned and 11 had incomplete data.

Attrition (final N): 62 women included in the analysis

Age: Mean +/- SD for each tertile of caloric intake:

Highest 34.6 +/- 4.9 years
Middle 34.8 +/- 4.4 years
Lowest 35.1 +/- 2.7 years

Ethnicity: Chinese women, not further specified

Other relevant demographics:

Anthropometrics: Tertiles similar in height, weight, BMI, and weight gain

Location: Queen Mary Hospital, Hong Kong, China

Summary of Results:

Variables

Highest (n=21)

Mean±SD

Middle (n=20)

Mean±SD

Lowest (n=21)

Mean±SD

Statistical Significance of Group Difference

OGTT (mmol/L)

Fasting

2 h

Gestation at OGTT (weeks)

4.7±0.5

9.1±1.8

19.4±8.5

4.6±0.4

8.9±0.9

16.5±7.6

4.7±0.6

9.2±1.5

20.9±7.4

Mean glucose concentration (mmol/L)

6.2±0.8*

5.6±0.6

5.9±0.9

<0.05

*NS=Not significant, Duncan's test p<0.05 compared with middle terile.

Other Findings

Mean daily calorie intake from highest to lowest tertile: 1863, 1692, 1384
There were no significant differences in maternal weight gain, length of gestation, birthweight, crown heel length, apgar score, %LGA, %SGA, or placental weight
Proportion of LGA (>90th percentile) was 16.1% and SGA (<10th percentile) was 14.5%

Author Conclusion:

Neither the postprandial blood glucose profile nor gestational weight gain in non-obese GDM women managed with diet therapy reflect their actual caloric intake. There was a tendency for patients to over-restrict their intake, and the prevalence of SGA infants was unexpectedly high. Nevertheleess, results suggest that apart from the incidence of SGA infants, the perinatal outcome remained satisfactory as long as the caloric intake did not exceed that prescribed.

Funding Source:

Reviewer Comments:

Diet surrounding days of blood glucose profile assessment not likely representative of usual diet intake
Only women in highest tertile came close to recommended intake per authors, so they did not have data to support conclusions regarding women who exceed recommended intake
Good control of potential confounding by energy needs to restrict sample to those prescribed 30 kcal/kg
Power calculations for differences in caloric intake but the outcome variable was blood glucose profile - unclear whether sample size was large enough to detect difference
Criteria for incomplete food records unclear
Unsure whether data abstractors were masked to calorie level
Funding source not specified

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.)	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?	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.)	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?		???
	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?	???
	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?	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?	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?	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?		???
	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?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	???
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?	No
	10.2.	Was the study free from apparent conflict of interest?	Yes