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Do We Know How to Find Gestational Diabetes Mellitus?

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Pathophysiology

Current Diagnosis Guideline

Discrepancies

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A carbohydrate intolerance of varying degrees and severity with onset or first recognition during pregnancy with a probable resolution after the end of pregnancy. Diabetes, glucose intolerance or insulin resistance may have existed before the pregnancy.

Gestational Diabetes Mellitus (GDM)

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Insulin resistance occurs because the hormonal changes associated with pregnancy partially block the effects of insulin.

Insulin resistance causes glucose to be shunted from the mother to the fetus to facilitate fetal growth and development.

During the third trimester of pregnancy, insulin resistance increases by 50%.

Pregnancy Pathophysiology

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Maternal pancreatic beta cells increase insulin secretion almost 3 fold to compensate for increased insulin resistance.

If the mother’s pancreas is unable to produce sufficient insulin to overcome insulin resistance, maternal glucose levels increase and GDM occurs.

GDM usually disappears after pregnancy because the hormonal changes that caused insulin resistance are no longer present.

Pregnancy Pathophysiology

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Management

Medical Nutrition therapy: nutrition restriction and reconstruction

Insulin Therapy

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Value of Laboratory Screening for GDM

Screening, identification and treatment can decrease the morbidity and mortality of GDM.

Decreased macrosomia, cesarean birth and birth trauma due to a > 4000g infant.

Decreased neonatal hypoglycemia, hypocalcemia, hyperbilirubinemia, polycythemia.

Identify women at future risk for diabetes and those with insulin resistance.

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Demographics of GDM

Most common medical complication of pregnancy

The prevalence may range from 1 to 14% of all pregnancies, depending on the

population studied and the diagnostic tests employed.

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Age <25 years

Weight normal before pregnancy

Member of an ethnic group with a low prevalence of GDM

No known diabetes in first-degree relatives

No history of abnormal glucose tolerance

No history of poor obstetric outcome

Low-risk Group:Requires no glucose testing, but this category is limited to those women meeting all of the following characteristics:

Who Should be Screened

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High Risk Group:Should undergo glucose testing as soon as feasible. If they are found not to have GDM at that initial screening, they should be retested

between 24 and 28 weeks of gestation.

Marked obesityPersonal history of GDMGlycosuriaA strong family history of diabetes

Who Should be Screened

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Women of average risk should have testing undertaken at 24–28 weeks of gestation.

Who Should be Screened

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Fasting plasma glucose

Diabetes

Casual plasma glucose

7.0 mmol/l(126 mg/dl)

11.1 mmol/l(200 mg/dl)

>

>

Screening

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Fasting plasma glucose

Two-step or one-step screening approach1. Glucose Challenge Test (GCT)2. Oral Glucose Tolerance Test (OGTT)

Casual plasma glucose

7.0 mmol/l(126 mg/dl)

11.1 mmol/l(200 mg/dl)

<

<

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Two-Step Screening

If >7.2-7.8mmol/l, proceed to diagnostic oral glucose tolerance test (OGTT).

If glucose level < 7.2-7.8mmol/l (130-140mg/dl)No further screening needed.

50g glucose challenge test (GCT)(non-fasting)1hr

Nearly 25 % of women will have a + 1hr GCT, and will need a OGTT.

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One-Step Screening

Directly proceed to diagnostic oral glucose tolerance test (OGTT).

The one-step approach may be cost-effective in high-risk patients or population.

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3-hr 100-g OGTT

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2-hr 75-g OGTT

9.9

8.1

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Skepticism

Developed in different population

Should we use the same cutoff concentrations?

2 out of 3 or 2 out of 4 thresholds?

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Pregnant women (16-20 weeks) (1017)

Perform 75g test

#227 g>7.2 mmol/l at 1hr

Perform 100g test (17-21 weeks)

#45 GDM. No further testing

#182 non-GDM. #790 with g<7.2mmol/l at 1hr

#972 pregnant women (26-30 weeks)

Perform 75g test

#484 with g>7.2mmol/l at 1hr #488 with g<7.2mmol/l at 1hr

No further testingPerform 100g test (27-31 weeks)

Flow Chart of Study Design

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16-21 weekspregnancy

100g test 75g test

26-31 weeks pregnancy

Number of diagnosed GDM

41 15

60 26 11

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Both Cohen index

0.21

0.18

0 disagreement0–0.2 weak agreement0.2– 0.4 fair agreement0.4 –0.8 good agreement0.8 –1.0 perfect agreement

McNemar

P<0.001

P<0.001

30 4

49 15

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The area under the curve of a continuous glucose profile for 3 h

Mixed meal tolerance tests

Different Approaches

Continuous glucose monitoring in the typical home setting for several days

Something other than glucose?

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What test best identifies glucose toxicity for the fetus?