Gestational diabetes Diabetes during pregnancy
Definition.
Gestational Diabetes Mellitus (GDM) is defined by abnormal Glucose Tolerance during
pregnancy; the Glucose Tolerance Test is normal before, and which is usually normal, after pregnancy.
 |
Gestational Diabetes Mellitus (GDM) is present in around 3-4% of all pregnancies. |
|
|
Gestational Diabetes Mellitus (GDM) can be associated with significant complications in fetus and newborn including higher fatality rate. |
|
|
Thus, it is important to rule out Gestational Diabetes in all pregnancies. If not feasible in all, at least all high risk patients must undergo the test. |
Low Risk Patients For Gestational Diabetes. (GDM)
 |
Pregnant women who fulfill all the criteria listed below, need not be screened for GDM. |
|
|
are < 25 years of age |
|
|
are a normal body weight |
|
|
have no family history (i.e. first degree relative) of diabetes. |
|
|
have no history of abnormal glucose metabolism. |
|
|
have no history of poor obstetric outcome. |
|
|
are not member of an ethnic/racial group with a high prevalence of diabetes. |
High Risk Patients For Gestational Diabetes. (GDM)
|
|
Women who had GDM during a previous pregnancy. |
|
|
Women with a first degree relative who is a diabetic. |
|
|
Women who gave birth to large weight babies in a previous pregnancy. |
|
|
Women whose newborn, in a previous pregnancy, showed any complication known to be associated as arising from maternal GDM. |
|
|
Women who gave birth to still born babies or infants with congenital abnormalities. |
|
|
Women with bad obstetric history, including recurrent fetal wastage, hypertension, eclampsia (a pregnancy associated illness with fits), etc. |
|
|
Women with repeated or persistent urinary tract infection. |
|
|
Women manifesting glycosuria (glucose positive in urine) during pregnancy. |
|
|
Women over the age of 30 years. |
Diagnosis of Gestational Diabetes.
Who should be screened for diabetes?
|
|
Ideally , all pregnant women should be tested to rule out Gestational Diabetes. |
|
|
All high risk patients must undergo the test. |
Timing of test:
|
|
Screening between 24-28 weeks in all pregnant women of average risk. |
|
|
Earlier as soon as possible, even at first initial visit, in patients with a high risk of GDM (marked obesity, personal history of GDM, glycosuria, or a strong family history of diabetes, or a bad obstetric history). If they are found not to have GDM at that initial screening, they should be retested between 24 and 28 weeks of gestation. |
Screening Methods for diagnosis of Gestational Diabetes.
|
|
Initial screening may be done by estimating the Fasting glucose levels and the levels 1 hour after an oral dose of 50 grams of glucose. |
|
|
This test can be done in the fasting state or at any time; in the latter case, only the one hour blood glucose value is taken into consideration for diagnosis. |
|
|
The criteria for abnormal glucose tolerance in pregnancy are those of Carpenter and Caustan, which is also recommended by ADA Fourth international workshop conference on gestational diabetes mellitus held in march 1977. |
Interpretation of results.
|
|
A fasting plasma glucose level >126 mg/dl (7.0 mmol /l) or a casual plasma glucose > 200 mg/dl (11.1 mmol/l) meets the threshold for diagnosis of diabetes. In such cases confirmation of the diagnosis precludes the need for any glucose challenge. |
|
|
In absence of this degree of hyperglycemia, evaluation for GDM in women with average or high-risk characteristics should follow one of two approaches. |
Carpenter and Caustan (modified O Sullivan and Mahan) Criteria
Diagnosis of GDM with a 100 g or 75 gm glucose load (Diagnostic OGTT)
|
|
Venous Plasma Glucose (mg/100 ml) |
Venous Plasma Glucose mmol/l) |
|
100 g glucose |
|
|
|
Fasting 1 hour 2 hour 3 hour |
95 180 155 140 |
5.30 10.00 8.60 7.80 |
|
75 g glucose |
|
|
|
Fasting 1 hour 2 hour |
95 180 155 |
5.30 10.00 8.60 |
|
Two or more of the venous plasma concentrations must be met or exceeded to make the positive diagnosis of gestational diabetes. The test should be done in the morning after an overnight fast of between 8 and 14 hrs and after at least 3 days of unrestricted diet (> or = 150 g carbohydrate per day)) and unlimited physical activity. The subject should remain seated and should not smoke throughout the test.
100 g OGTT is better validated test as compared to 75 g test. |
||
One step approach
|
|
Perform a diagnostic OGTT (Oral Glucose Tolerance Test) without prior plasma or serum glucose screening. The one step approach may be cost -effective in high risk patients or populations. |
|
50 g glucose |
Venous Plasma Glucose (mg/100 ml) |
Venous Plasma Glucose (mmol/l) |
Followed by diagnostic OGTT- % of diagnosis |
|
1 hour 1 hour |
>140 >130 |
>7.8 >7.2 |
80 90 |
Two step approach
|
|
Perform an initial screening by measuring the plasma or serum glucose concentration 1 hr after a 50-g oral glucose load (glucose challenge test -GCT) and perform a diagnostic OGTT on that subset of women exceeding the glucose threshold value on the GCT. |
|
|
When a 2 step approach is used, a glucose threshold value >140 mg/dl (7.8 mmol/l) identifies 80 % of women with GDM, and the yield is further increased to 90 % by using a cutoff of > 130 mg/dl (7.2 mmol/l) |
|
|
With either approach, the diagnosis of GDM is based on OGTT. |
Older criteria of diagnosis
Comprehensive tests for GDM
The Comprehensive test is same as for diagnosis of diabetes in non pregnant persons, but the criteria differ.
|
|
As per W.H.O.criteria, in addition to the blood glucose levels in the diabetic range, values suggestive of I.G.T (Impaired glucose tolerance)., seen in a pregnant woman, must also be taken as diagnostic of Gestational Diabetes. |
|
|
Many centers still use the O'Sullivan Criteria. |
O Sullivan and Mahan Criteria
|
|
In this test, blood is collected in the fasting state and then at 1, 2, and 3 hours intervals after an oral load of 100 grams of glucose. |
|
|
The presence of Gestational Diabetes is diagnosed according to the following criteria: |
O Sullivan Criteria
Venous Plasma Glucose (mg/100 ml) |
Venous Whole Blood Glucose (mg/100 ml) | |
Fasting 1 hour 2 hour 3 hour |
105 190 165 145 |
90 165 145 125 |
|
Two or more of the above values must be met or exceeded to make the diagnosis of gestational diabetes | ||
Interpretation of results.
Two of the four values must be met to diagnose GDM.
Significance of GDM
|
|
Women with GDM may go on to have Diabetes in later life. |
|
|
They must be considered as having high risk for the development of Diabetes and must undergo annual testing. |