GDM: Monitoring (2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To assess the 24-hour glucose levels in a group of nondiabetic, nonobese pregnant women and to verify the presence of correlations between maternal glucose levels and sonographic parameters of fetal growth.

Inclusion Criteria:
  • Caucasian
  • Singleton pregnancy
  • Gestational age confirmed by first-trimester ultrasound.
  • Normal OGTT between 24 and 28 wk gestation:  1-hr glucose <135 mg/dl
  • Number of previous deliveries <2
  • Pregestational BMI: 19-25
  • Delivered at term
  • Delivered healthy infant
Exclusion Criteria:
  • Chronic hypertension
  • GDM in previous pregnancy
  • Taking medications that would affect glucose metabolism: steroids, b2 – sympathomimetics
Description of Study Protocol:


From June 1998 to December 1999, 66 pregnant women who were receiving prenatal care as an outpatient at the Perinatal Medicine Unit of the University of Florence, Italy were enrolled in the study.

Design:  Cohort Study

Blinding Used (if applicable):  not applicable

Intervention (if applicable):  (28-38 wk gestation)

1. Self-selected meals at 8 a.m., 12 p.m., and 8 p.m.

2. Self-blood glucose monitoring

  • before meals
  • 1 to 2-hr after meals
  • q 2-hr in the afternoon
  • during the night

3.  Fetal ultrasound scan at 22, 28, 32 and 36 wk gestation.

Statistical Analysis

Correlations between daily glucose profiles and ultrasound fetal parameters were estimated using Pearson's correlation coefficient.  One-way ANOVA was used to test for trends of overall glycemic values throughout gestation.

Data Collection Summary:

Timing of Measurements:

Mean daily blood glucose between 28 and 38 wks gestation.  Fetal ultrasound scan at 22, 28, 32 and 36 wk gestation.

Dependent Variables

  • Mean daily blood glucose between 28 and 38 wks gestation.

Independent Variables

1.  Self-selected meals at 8 a.m., 12 p.m., and 8 p.m.

2.  Self-blood glucose monitoring

  • before meals
  • 1 to 2-hr after meals
  • q 2-hr in the afternoon
  • during the night

3.  Fetal ultrasound scan

4.  Subject compliance: percentage of the 30 glucose measures that were actually performed during the 4 wk study.

  • LGA: >90% percentile
  • SGA:<10th percentile

Control Variables


Description of Actual Data Sample:

Initial N:  66 enrolled

Attrition (final N):  51 women met the study criteria and completed the study. 7 women of the 66 discontinued blood glucose monitoring.

Age:  mean age 30 years

Ethnicity:  all Caucasian

Other relevant demographics:


Location:  Italy

Summary of Results:

Maternal and neonatal characteristics:


Age, y 30.0 (20-40)
Parity 1    (0-2)
BMI  21.0  (18-25)
1-hr OGTT, mg/dl 115.8 +15.7
Daily glucose, mg/dl 74.7+5.2
Compliance, % 96.9+2.0
Weight gain, kg 8.7  (7-12)
Gestational age, wk 40   (37-42)
Birth weight, g  3,301.5+351.6
LGA 4   (7.8)
SGA 3   (5.9)

Diurnal blood glucose profile


28 wk 38 wk
0800 54.8+6.2 59.0+4.1
0900 92.0+7.5 104.2+5.1*


78.2+5.8 89.2+9.5
1200 67.1+5.5 64.2+6.2
1300 92.9+7.1* 105.2+4.9*
1400 85.2+4.9  95.0+6.2*


70.1+5.8 68.2+6.1


63.0+6.5  66.2+5.0


62.4+4.1 65.1+7.7


91.1+7.8* 105.2+4.0*
2200 79.5+6.3  95.2+4.2*
0000 64.5+5.1 69.2+7.0


60.5+3.9 66.2+4.6


59.8+3.4 63.1+3.8


58.7+6.0  60.1+5.4

*Significant correlation with fetal ultrasound measurements

Other Findings 

The daily mean glucose level during the third trimester was 74.7+5.2 mg/dl.  Daily mean glucose values increased between 28 (71.9+5.7 mg/dl) and 38 (78.3+5.4 mg/dl) wk gestation. 

There was a significant positive correlation at 28 wk between 1-hr postprandial glucose values and fetal abdominal circumference (AC).  At 32 weeks, we documented positive correlations between fetal AC and maternal blood glucose levels 1 hr after breakfast, 1 and 2 hour after lunch and 1 and 2 hour after dinner.

At 36 wk, there was a positive correlation between fetal AC and 1 and 2-hr postprandial blood glucose levels. 

Also, there was a negative correlation between head circumference ratio and 1-hr postprandial blood glucose values.

Author Conclusion:

This longitudinal study provides a contribution toward the definition of normoglycemia in nondiabetic, nonobese pregnant women, moreover, it reveals significant correlations of postprandial blood glucose levels with the growth of insulin-sensitive fetal tissues and, in particular, between 1-h postprandial blood glucose values and fetal abdominal circumference. 

The variability of postprandial glucose values as assessed by the SD is generally greater in the morning.

These findings are in agreement with those of diabetic pregnancies in which a 1-hr postprandial maternal blood glucose concentration in the third trimester is considered a strong predictor of infant birth weight and fetal macrosomia.

Funding Source:
University/Hospital: University of Florence (Italy)
Reviewer Comments:

This study documents that the lowest blood glucose is in the morning and the greatest variability in blood glucose after breakfast, Those with GDM may limit variability by limiting carbohydrate at breakfast. Since the highest rise in blood glucose after meals is in the first hour, this is the optimal time for SBGM.

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) 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? Yes
  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? Yes
  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? Yes
  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? 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? 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? 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? 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