EAL

GDM: Medical Nutrition Therapy (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

(1) to evaluate fetal and placental anthropometric parameters in pregnancies associated with gestational diabetes diagnosed at the beginning of the third trimester

(2) to study whether fetal weight, fetal length and placental weight are related to maternal characteristics such as BMI, response to oral glucose tolerance test and glycemic control in GDM pregnancies.

Inclusion Criteria:

Cases: GDM diagnosis by OGTT

Controls:

non smoking
women with a negative 50 g oral glucose challenge test (OGCT)
no obstetrical complications

Exclusion Criteria:

None specified.

Description of Study Protocol:

Recruitment

One hundred and thirty-two pregnancies complicated by gestational diabetes were recruited at the time of diagnosis between 28 and 32 weeks of gestation and compared to 143 consecutive normal pregnancies (N)

Design

Cases and controls were compared on maternal and fetal characteristics.

Blinding used (if applicable): None described

Intervention (if applicable): Not applicable

Statistical Analysis

Unpaired two tailed t tests
Linear and exponential regression
Fisher chi-square test to analyse the distribution in birthweights in the two groups.

Data Collection Summary:

Timing of Measurements

Only specification was that recruitment occurred at time of diagnosis (28-32 weeks) for cases

Dependent Variables

Maternal characteristics (age, race, prepregnancy weight, BMI, weight gain during pregnancies, parity, education level, social occupation)
Neonatal data (gestational age, APGAR score, sex, weight, length)
Ponderal Index (PI) was calculated as fetal weight/(fetal length)

3*100.

Dependent Variables

OGCT was performed between 24 and 28 weeks of gestation and was considered negative with plasma glucose after 1 h<140 g/dl.
GDM was diagnosed in the presence of a 100 g oral glucose tolerance test (OGTT) with two or more values over the ranges established by Carpenter and Coustan (1982) (plasma glucose*1 h<180 g/dl 2 h<155 g/dl 3 h<140 g/dl). The mean glucose value was calculated as the mean plasma glucose after OGTT (1 h+2 h+3 h)/3 (OGTT mean).

Control Variables

Gestational age -calculated from the last menstrual period and confirmed by confirmed by a routine ultrasonographic exam at 20 weeks of gestation.

Description of Actual Data Sample:

Initial N: 143 controls and 132 cases

Attrition (final N): none specified

Age: Cases were older than controls (33.2 (SD 4.5) vs 30.6 (SD 5.4) yr, p<0.001)

Ethnicity: not specified

Other relevant demographics:

Anthropometrics Cases had a significantly higher BMI and higher pre-pregnancy weight but did not statistically differ in their amount of weight gain.

Location: Sao Paolo Hospital, Milan Italy

Summary of Results:

Variables	Cases Mean±SD	Controls Mean±SD	Statistical Significance of Group Difference
Gestational Age, wk	38.6±1.39	39.3±1.17	p<0.05
Birthweight, g	3287±474	3274±296	p<0.05 after controlling for gestational age
Placental Weight, g	592.20±115.77	561.86±88.53	p<0.01

Other Findings

OGTT-2h was slightly negatively correlated with fetal weight (r² = 0.063, p<0.001) and placental weight (r² = 0.036, p<0.05)

Author Conclusion:

Treatment of gestational diabetes is able to modulate fetal weight proportionally more than placental weight and that fetal and placental growth are more influenced in those GDM pregnancies with the highest degree of glucose intolerance.

Funding Source:

Reviewer Comments:

Control group excluded smokers which could influence birthweight but no data were provided on smoking status of GDM cases
Did not have comparison group of GDM cases that did not receive treatment, so it is difficult to attribute findings to treatment of GDM
Data collection procedures unclear - were they from medical records or standardized for the study; were data collectors masked to condition?

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)	N/A
	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)	N/A

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?	Yes
	2.2.	Were criteria applied equally to all study groups?	No
	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?		???
	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?	No
	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?	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.)	???
	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?		No
	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.)	???
	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?	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?		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?	No
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	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?	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?	N/A
	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?	???
	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?	???
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?	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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes