EAL

GDM: Prevention of GDM Diagnosis (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

This study was performed to determine whether the prevalence of GDM is influenced by iron deficiency anemia.

Inclusion Criteria:

singleton pregnancy coded as having antenatal anemia and all those delivering within a 24 month period, according to the annual statistics.
diagnosis of of iron deficiency confirmed by iron studies
electrophoresis studies
and/or response to to iron therapy and booking before 20 weeks' gestation

Exclusion Criteria:

Women with other causes of anemia such as thalassemia trait and those who had late bookings or delivered elsewhere.

Description of Study Protocol:

Recruitment : Retrospective case-control study, subjects retrieved from the annual statistics.

Design : Retrospective Case Control Study

Blinding used (if applicable): not applicable

Intervention (if applicable): not applicable

Statistical Analysis

Categorical variables were compared with the X² test
Correlations between the prevalence of GDM was tested was tested by Pearson's correlation.
Odds ratios (ORs) with 95% CI were generated
Continuous variables that are normally distributed were expressed as means ± SD and tested by the Student's t test.
Statistical calculation was performed using a commercial computer package (Statistical Package for Social Sciences for Windows version 10.0; SPSS, Chicago, Il)

Data Collection Summary:

Timing of Measurements

Dependent Variables

Age (years)
Height (cm)
Weight (kg) - prepregnancy, predelivery, increment
BMI (kg/m²) - prepregnancy, predelivery, increment
MCV (fl) - booking, third trimester, predelivery
Anemia group: (Group 1 - anemia at booking and third trimester; Group 2 - anemia before the third trimester; and Group 3 - anemic only in the third trimester) - patients with less than hemoglobin level of <10g/dl at any time during pregnancy were considered anemic.

Independent Variables

Maternal age (years)
Multiparas (%)
Height (cm)
Weight (kg) - prepregnancy, predelivery
BMI (kg/m²) - prepregnant, predelivery
BMI increment (kg/m²)
Incidence of GDM (%)
Infant gestation (weeks)
Birth weight (g)
Crown heel length (cm)
BMI (kg/m²)
Apgar score - at 1 minute, at 5 min
Incidence of LGA (%)
Incidence of SGA (%)

Control Variables

Description of Actual Data Sample:

Initial N: 728

Attrition (final N): 728

Age: See Table 1

Ethnicity: Chinese (95%)

Other relevant demographics:

Anthropometrics

Location: Department of Obstetrics and Gynecology, Queen Mary Hospital, Hong Kong, China and the University of Hong Kong, Hong Kong , China.

Summary of Results:

The study group of 242 women was shorter, had lower predelivery weight and BMI with concomitant decreased gestational weight gain and BMI increment, and had more multiparas but a lower prevalence of GDM (OR 0.52, 95% CI 0.27-0.97). (Table 1) .

Table 1: Maternal and infant charcteristics between the anemic and nonanemic groups

	Anemic	Nonanemic	P
n	242	484	-
Maternal age (years)	27.9±5.4	28.4±4.8	NS
Multiparas (%)*	55.6	45.3	0.009
Height (cm)	152.6±5.8	155.4±5.3	<0.0001
Weight (kg)
Prepregnancy	51.6±9.2	51.9±7.1	NS
Predelivery	61.7±9.7	65.0±8.4	<0.0001
Weight gain (kg)	10.4±4.4	13.1±4.4	<0.0001
BMI (kg/m²)	-	-	-
Prepregnancy	21.9±2.6	21.5±2.7	0.051
Predelivery	26.4±3.0	26.9±3.2	0.034
BMI increment (kg/m²)	4.5±2.0	5.4±1.8	<0.0001
Incidence of GDM (%)*	5.3	9.8	0.038
Infant gestation (weeks)	38.8±1.8	39.1±1.5	NS
Birth weight (g)	3,236±438	3,169±447	0.053
Crown heel length (cm)	50.3±2.2	49.7±2.6	NS
BMI(kg/m²)	12.8±1.5	12.8±1.2	NS
Apgar score	-	-	-
At 1 min	8.8±1.1	8.7±1.2	NS
At 5 min	9.8±0.5	9.8±0.8	NS
Incidence of LGA (%)*	21.5	12.8	0.002
Incidence of SGA (1%)*	4.1	7.5	0.073

Data are means ± SD or percent. Analysis was performed by Students test or X² test(indicated by asterisks).

Among the sub-categories (Group 1 - anemia at booking and third trimester; Group 2 -anemia before the third trimester; and Group 3 - anemic only in the third trimester), all three anemic subgroups accounted for the significant differences in weight and BMI increments among the anemic and control groups (Table 2).

Table 2: Maternal characteristics according to duration of anemia

	<<	Anemia Groups	>>
	Group 1	Group2	Group 3	Control Group	P
n	104	17	121	484	-
Age (years)	26.6±5.4*€¶	29.7±5.9	28.8±5.1	28.6±4.8	0.001
Height (cm)	152.0±5.9*	153.8±7.1	152.9±5.4	155.4±5.3	<0.0001
Weight (kg)
Prepregnancy	50.8±9.5	52.3±11.4	52.3±8.7	51.9±7.1	NS
Predelivery	60.5±9.4*	62.9±12.3	62.9±12.3	65.0±8.4	<0.0001
Increment	10.0±4.5*	10.6±6.1*	10.7± 4.1*	13.1±4.4	<0.0001
BMI (kg/m²)
Prepregnancy	21.7±2.6	21.9±3.2	22.2±2.6	21.5±2.7	NS
Predelivery	26.1±2.8	26.4±3.9	26.7±3.0	26.9±3.2	NS
Increment	4.4±2.0*	4.5±2.7*	4.6±1.8*	5.4±1.8	<0.0001
MCV (fl)booking	82.1±10.5* ¶	83.5±11.6*	85.8±6.4*	89.6±3.9	<0.0001
Third trimester	79.4±9.7* ¶	82.6±13.5*	85.6±8.0*	92.0±8.4	<0.0001
Predelivery	81.1±10.2* €	85.4±12.7	84.5±7.3*	88.8±6.3	<0.0001

Data are means ±SD. Please refer to text for definition of anemic groups. MCV, mean cell volume. Analysis was performed by one-way ANOVA with post hoc analysis by Duncan's test: *P<0.05 with control group;€ P<0.05 with group 2; ¶ P<0.05 with group 3.

Other Findings

There were significant differences in the MCV among all groups in the three measurements.
On further analysis, a significant inverse correlation was found between the prevalence of GDM with severity and duration of anemia (r=-0.074,P=0.045) 3.78% in group 1, 5.9% in group 2, 7.4% in group 3, and 9.8% in the control group.

Author Conclusion:

The prevalence of GDM is reduced in iron deficiency anemia, which probably served as a surrogate for other factors such as nutritional inadequacy and reduced gestational weight gain.

Limitations:

In the developing world, overall nutritional improvement and correction of anemia could be contributing factors to the increasing prevalence of diabetes and GDM.
Because the obstetric population was of the same ethnic background and culture , different dietary habits were unlikely to have played an important role in the findings, especially when vegtarians were excluded.

Funding Source:

University/Hospital:

Queen Mary Hospital, University of Hong Kong (both China)

Reviewer Comments:

A retrospective study looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. Most sources of error due to confounding and bias are more common in retrospective studies than in prospective studies .

The limitations and critique of the study, as stated by the authors appear to be very appropriate. The critique of note was its relevance in the developing world.

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?	???
	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?		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?	???
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?	???
	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?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	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?		N/A
	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?	N/A
	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?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	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?	N/A
	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)?	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?	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?		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