EAL

GDM: Abnormal Glucose Tolerance During Pregnancy (2008)

Citation:

Study Design:

Class:

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Quality Rating:

Research Purpose:

The clinical significance of large placentas in diabetic pregnancies is not known. A retrospective study was performed to determine whether a disproportionately large placenta, as represented by a high ratio of placental weight to birth weight (placental ratio), in pregnancies complicated by the World Health Organization category of impaired glucose tolerance (IGT) was associated with perinatal morbidity.

Inclusion Criteria:

The case records of all patients with singleton pregnancies complicated by IGT and delivered during a 3-year period. The placental ratio was calculated as the placental weight divided by the birthweight. The cases with a placental ratio more than the mean plus one standard deviation (ratio >0.2095) based on the values established (in previous studies) were considered to have a high ratio and constituted the study group, while the other cases constituted the comparison group.

Exclusion Criteria:

The exclusion criteria was not described.

Description of Study Protocol:

Recruitment Method was not detailed

Design Historical cohort

Blinding used (if applicable): not applicable

Intervention

Patients with GDM were referred to a dietitian and put on dietary control (30 kcal/kg) initially.
Insulin therapy was given if dietary readjustment failed to maintain the fasting glucose level less than 6.0 mmol/L or postprandial glucose less than 7.1 mmol/L.
HbA1c level was measured after diagnosis to exclude preexisting but undiagnosed diabetes mellitus.
During pregnancy all obstetric patients were treated according to established departmental protocols.
Routine ultrasound examination was done at 18-20 weeks to confirm the maturity and to exclude fetal anomalies.
A proprietary preparation of multivitamins and iron supplements (with 29 mg of elemental iron) is given to all patients.
Labor induction and cesarean delivery were performed based on medical indications.
High-risk pregnancies received regular fetal monitoring with the nonstress test and ultrasound assessment, and intrapartum electronic fetal heart rate monitoring is applied to all patients.
After delivery, for all complicated pregnancies or cases of suspected fetal distress, pediatricians attended the delivery.
In all cases, infants were examined after delivery and the maturity confirmed by the pediatricians.
After delivery of the placenta, it was washed in a sink to clear away any blood and meconium before it is examined on a corrugated board besides the sink.
After examination, the entire placenta, including the membranes and the attached segment of cord, was placed in a plastic container for weighing in on an electronic scale, with the weight of the container calibrated beforehand.

Statistical Analysis

Student t test was used for continuous variables, which were expressed as mean and 95% confidence interval (CI) of the difference in the mean values between the two groups as calculated by the statistics program.
Categorical variables were compared with the X² or Fisher exact test for categoric variables, and Pearson correlation (r).
The statistical calculations were performed using a commercially available package(SPSS/PC; SPSS Inc., Chicago, IL).

Data Collection Summary:

Timing of Measurements: as below

Dependent Variables

Diagnostic criteria

The study used the World Health Organization 75-g OGTT for the diagnosis of GDM, which includes both the categories of IGT and diabetes mellitus
The OGTT is arranged for all antenatal patients with risk factors, such as relevant family history or past obstetrical history, maternal age over 34 years, weight of 75kg or more, and abnormal findings during the antenatal visits such as recurrent glycosuria, suspected polyhydramnios, or fetal size greater than estimated gestational age.
A routine random glucose screening is performed at 28-30 weeks’ gestation for low risk patients , and those with elevated random glucose (>5.8 mmol/L if < hours postprandial, and >5.0 mmol/L if 2 hours postprandial) will also have the OGTT.
More than 95% of the gestational diabetes patients had had IGT.

Perinatal Outcome

Low Apgar scores at the first and fifth minutes of life
Metabolic complication (hypoglycemia, hypocalcemia, hypomagnesemia)
Hyper bilirubinemia resulting in jaundice requiring phototherapy or exchange transfusion
Bacteriological confirmed infections and clinical sepsis that required antimicrobial treatment
Respiratory complications (respiratory distress syndrome, pneumothorax, meconum aspiration), neurological complications
perinatal mortality
LGA birth weight >90^th percentile based on local percentile chart)
SGA (birthweight < 10th percentile).

Independent Variables

Maternal demographics –including calculated body weight (BMI)
Parameters of glycemic control
Perinatal complications reported previously

Control Variables

Description of Actual Data Sample:

Initial N: 1472 pregnant women

Attrition (final N): 1472 women

Age: See Table 1

Ethnicity:

Other relevant demographics:

Anthropometrics:

There was no difference in the maternal age, height, or weight between the two groups, although the prepregnancy BMI was slightly but significantly higher in the study group.

Location: The Department of Obstetrics and Gynecology, The University of Hong Kong and the Department of Obstetrics and Gynecology, Tsan Yuk Hospital, Hong Kong, People’s Republic of China.

Summary of Results:

There was no difference in the maternal age, height, or weight between the two groups, although the prepregnancy BMI was slightly but significantly higher in the study group (Table I).

Table 1. Maternal Characteristics in Relation to Placental Ratio

-	Study group(n=400)	Control group(n=1072)	95% CI difference
Age (years)*	32.2	31.9	-0.236, 0.852
Height (cm)*	154.4	154.9	-1.119, 0.122
Weight (kg)*	-	-	-
Prepregnant	55.5	54.7	-0.202, 1.857
At delivery	66.2	65.8	-0.677, 1.457
Gain	10.6	11.0	-0.960, 0.123
Body mass index(kg/m² )*	-	-	-
Prepregnant	23.3 ¶	22.8	0.062, 0.882
At delivery	27.8	27.4	-0.103, 0.731
Increment	4.5	4.6	-0.378, 0.065
OGTT result (mmol/L)*	-	-	-
Fasting	4.7 ♦	4.6	0.003, 0.117
2-hour	9.0	8.9	-0.007, 0.167
Postprandial glucose	-	-	-
(mmol/L)*	-	-	-
First series	6.2	6.1	-0.195, 0.274
Last series	5.9		-0.135, 0.045
HbA1c (%)*	4.7	4.7	-0.153, 0.149
Pregnancy-induced	-	-	-
Hypertension(%) £	4.8	6.7	-
Antepartum hemorrhage(%) £	9.3	6.7	-
Cesarean delivery (%) £	18.8	15.8	-

* Results in mean and 95% CI of the difference, compared by t test.

¶ P= .024

♦ P=.040

£ Results in percentage and comparison by x² test.

The infants in the study group had slightly but significantly younger gestational age, lower birth weight, and lower BMI (Table 2).

Table 2. Infant Outcome in Relation to Placental Ratio

-	Study group(n=400)	Control group (n=1072)	95% CI difference
Gestation (wk)	38.3*	39.0	-0.916.-0.418
Preterm births (%)	12.0 ¶	4.3	…
Birthweight (g)	3108*	3256	-211.5-84.5
Crown-heel length (cm)	50.0	50.3	-0.583,0.015
Body mass index (kg/m ² )	12.5*	12.8	-0.518-0.172
Placenta weight (g)	722*	583	124.2,152.6

Results expressed as mean, 95% CI difference except for preterm births.

*t-test P< .0001

¶ X² test P < .0001.

Although there was no difference in the incidence of SGA or LGA infants, the study group had a higher overall morbidity rate (OR 1.49, 95% CI 1.16, 1.91(Table 3).

Table 3. Perinatal Complications in Relation to Placental Ratio

-	Study group (n=400)	Control group (n=1072)	P
Small- for-gestational age	7.1	5.0	NS
Large-for –gestational age	18.6	20.4	NS
Overall morbidity rate	34.2	25.8	.0015
Apgar score <7	-	-	-
at 1 minute	9.3	5.4	.0082
at 5 minutes	2.0	1.0	NS
Apgar score <4	-	-	-
at 1 minute	2.0	1.3	NS
at 5 minutes	1.3	0.5	NS
Metabolic complications (total)	2.8	1.9	NS
Hypoglycemia	2.0	1.0	NS
Hypocalcemia	0.3	0.6	NS
Hypomagnesia	0.3	0	NS
Combined	0.3	0.3	NS
Treated for jaundice	18.6	14.0	.028
Perinatal infection	10.8	5.2	.00012
Respiratory complications	6.1	1.7	.00001
Neurological complications	1.0	0.6	NS
Birth trauma	1.3	1.1	NS
Perinatal mortality	1.3	0.6	NS

NS= not significant

Results expressed as percentage

Other Findings

Author Conclusion:

The placental ratio in pregnancies complicated by IGT was unrelated to maternal characteristics or glycemic status, but a high ratio was associated with increased perinatal morbidity.

Limitation

There is controversy about the association between GDM and increased placental ratio. It is likely that GDM is only one of the conditions that can result in a disproportionably large placenta.

Funding Source:

Reviewer Comments:

In a historical cohort study, data on exposure and occurrence of disease are collected after the events have taken place—the cohorts of exposed and non-exposed subjects are assembled from existing records, or health care registries. Studies of this kind provide a better opportunity than one time cross sectional studies to examine whether certain behaviors do in fact lead to (or cause) the disease.

The limitations and critique of the study, as stated by the authors appear to be very appropriate.

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.)	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?	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?		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?		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?	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?	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?		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?		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