Diabetes Mellitus:- Part 4 – Gestational Diabetes Mellitus, Oral glucose tolerance test, (OGTT)

December 17, 2021Chemical pathologyLab Tests

Gestational Diabetes Mellitus

Samples 

1. The patient is advised to come to the laboratory in a fasting state, where after taking a fasting blood sample, the patient is given 75 grams of glucose.
2. It is better to give glucose in 7-up where it will be well tolerated.
3. Collect fasting blood and then collect blood samples at 30, 60, 90, 120 minutes.
4. Multiple samples are taken at half-hour intervals along with the urine sample.
5. In pregnant lady collect blood at 60, 120, and  180 min after glucose.
6. Some time the sample is taken at 1, 2, 3, and up to 4 hours.

Purpose of the test (Indications)

1. To confirm the diagnosis of gestational diabetes.
2. It is used to diagnose Diabetes mellitus.
3. It is also used to evaluate hypoglycemia.
4. Patient with family H/o diabetes.
5. patients with obesity.
6. Patients with H/O recurrent infection.
7. Patients with H/O delayed wound healing.
8. Ladies with H/O stillbirths or delivering obese babies.
9. Patients with H/O random glycosuria, or hyperglycemia during pregnancy or after myocardial infarction, surgery, or stress.

Precautions

1. Advice to the patient to take >150 grams of the carbohydrates in the diet in the last 3 days before the test.
2. Stop these drugs at least 3 days before the test are hormone, contraceptives, steroids, salicylates, and anti-inflammatory drugs.
3. Stop the diuretics, hypoglycemic agents, antihypertensive drugs, and anticonvulsants.
4. Stress can increase the glucose level.
5. If the patient does not tolerate the glucose and vomits out, that may give a false result.
6. Avoid glucose tolerance tests in the following conditions:
   1. If there is persistent fasting hyperglycemia >140 mg/dL (>7.8 mmol/L).
   2. In case if there is a normal fasting glucose level.
   3. Patient with known diabetes mellitus.
7. In case if two hours glucose >200 mg/dL (>11.1 mmol/L).

Indications for the diagnosis of Gestation Diabetes Mellitus

1. This is recommended that screening should be done on all pregnant women between 24  and 28 weeks of gestation.
2. This should be advised for women at the age of 25 years or older.
3. Also advised before the age of 25 years if the women are obese or there is a family history of DM.

Gestational diabetes mellitus (GDM)

Pathophysiology

Definition

1. Gestational diabetes mellitus is defined as any degree of glucose intolerance which is seen during pregnancy.
   1. Usually seen around 24 weeks of gestation.
2. GDM can also be defined as hyperglycemia that develops the first time during pregnancy. This may be seen in 4% of pregnant ladies.

Pathophysiology of gestational diabetes mellitus

1. A normal pregnancy is associated with increased insulin resistance, especially in the late second and third trimesters.
2. This will occur in those pregnant ladies who can not maintain a sufficient level of insulin.
3. The risk factors are:
   1. Family history of the first-degree relative with diabetes mellitus.
   2. In obese ladies.
   3. In the case of late maternal age, usually after the age of 40 years.
   4. If there is glycosuria.
   5. Bad previous delivery history like stillbirth and macrosomia.
4. Screening should be performed between 24 to 28 weeks of gestation.
5. 3% to8% of pregnant women have gestational diabetes.

Complications of gestational diabetes mellitus:

5. The detection of early GDM will reduce the risk of prenatal fatal outcomes like:
   1. Excessive fetal growth.
   2. Birth trauma.
   3. Fetal morbidity.

Screening gestational diabetes mellitus(GDM) during pregnancy:

1. It can be assessed by a one-hour blood glucose level if it is >140 mg/dL.  Then advise OGTT for three hours.
2. O’Sullivan test is one-hour glucose after 50 grams of oral glucose intake.
3. Screening for the GDM advises OGTT with 50 grams of glucose.
4. Check the one-hour glucose level, which is called the O’Sullivan test.
5. Screening should be done between 24 to 28 weeks of gestation.
6. If one hour sample is >140 mg/dL, then taking a 3-hour 100-grams of glucose(OGTT) is necessary.
   1. Normal pregnancy is associated with increased insulin resistance, especially in the second and third trimesters.

Screening of gestational diabetes mellitus during the postpartum period:

1. If the results are abnormal during pregnancy then take OGTT postpartum.
2. If postpartum OGTT is normal then label diabetes mellitus during pregnancy.
   1. Check blood glucose on every visit because of the increased risk of diabetes mellitus, which is 30% during the next 5 to 10 years.
3. If postpartum OGTT  is abnormal, label these patients as Impaired glucose tolerance (IGT), or Impaired fasting glucose (IFG), which can happen in ∼5% to 10%.
   1. Another possibility is a clear-cut case of diabetes mellitus which can occur in 10% of the cases.
   2. The rest of the ladies are normal and they may develop diabetes mellitus in the next 5 to 10 years.

Risk factors include:

5. A family history of diabetes in first-degree relatives.
6. Obesity.
7. Advanced maternal age.
8. Glycosuria.
9. A selected bad outcome in the last pregnancy like stillbirth or macrosomia.

Modified criteria for the diagnosis of GDM include:

1. Low-risk patients are:
   1. Below the age of 25 years.
   2. Normal weight before the pregnancy.
   3. The ethnic group with a low incidence of GDM.
   4. No known first-degree relative with diabetes mellitus.
   5. No history of poor obstetric outcome.
   6.  There is no history of abnormal glucose tolerance.
2. Average-risk patients are:
   1. All those patients fall between low and high-risk patients.
   2. They should be tested between 24 to 28 weeks of gestation.
3. High-risk patients are:
   1. Marked obesity.
   2. Glycosuria.
   3. History of GDM.
   4. Strong family history of diabetes mellitus.

Important facts for Gestational diabetes mellitus (GDM):

1. OGTT is not recommended to see the complications of Diabetes mellitus.
2. Its use is also discouraged for fasting hypoglycemia.
3. In non-pregnant ladies and children, the OGTT is not recommended as a screening test.
4. For a pregnant lady 50 G glucose is recommended for screening.
5. The serum glucose level of >150 mg/dl at 1 hour, is considered for further testing.
6. There is a rapid response to insulin to oral glucose and the peak is 30 and 60 minutes.
7. Glucose comes to normal in 3 hours.
8. Glucose will not appear in the urine in a normal pattern.

Procedure for Oral glucose tolerance test (OGTT):

1. Record patient weight.
   1. The pediatric dose for glucose amount is based on their weight, calculated as 1.75 g/Kg, and should not exceed a total of 75 grams.
   2. Pregnant ladies can be given 100 grams.
   3. Can perform the test in pregnant ladies with 50 grams of glucose.
   4. Non-pregnant ladies can be given 75 grams.
2. Take the fasting blood for fasting glucose levels.
3. Give glucose (Glaxo’s-D) 75 to 100 grams in 5 minutes.
4. To pregnant ladies can perform the test with 50 grams of glucose.
5. Now take the blood 30, 60, 90. 120,  and 180 minutes (some books recommend 30, one hour, 2 hours, and 3 hours) after the intake of glucose.
6. To check the hypoglycemia advice 4 hours sample.
7. Also, take the urine sample with every blood sample.

Procedure for collection of the blood and urine during OGTT:

Normal values of glucose

Source 1

1. NORMAL WHEN
   1. Fasting glucose = < 110 mg/dl.
   2. Random glucose = < 140 mg/dl.
2. Child fasting = <130 mg/dl.
   • at 120 min = < 140 mg/dl.
   • Impaired glucose tolerance in children:
   • Fasting = <140 mg/dl.
   • 120 min = >140 mg/dl.

Adult non-pregnant OGTT result:

• • Fasting = 79 to 105 mg/dl.
  • 30 min = 110 to 179 mg/dl
  • 60 min = 120 to 170 mg/dl
  • 90 min = 100 to 140 mg/dl
  • 120 min = 70 to 120 mg/dl
  • All urine sample are negative.
  • >60 years  fasting = 70 to 115 mg/dL

Gestational diabetes  normal one hour = <140 mg/dL

1. Diabetes Mellitus when:
   1. Fasting glucose = 126 mg/dl or above
   2. Postprandial glucose = 200 mg/dl or above
   3. Random glucose more than 200 mg/dl with H/o polyuria, polydipsia, ketonuria, and weight loss.
2. IMPAIRED GLUCOSE when:
   1. Impaired fasting Glucose = 110 to <126 mg/dl
   2. Impaired glucose tolerance = 140 to <200 mg/dl

Source 2

Normal values of OGTT in Adult:

OGTT values in gestational diabetes mellitus (GDM):

• At least two values of  OGTT must exceed the following values for GDM:
  • High glucose level persists throughout the test.

At least two values must meet or exceed the following  values for GDM based on the oral glucose tolerance test:

Criteria for the positive 100 grams (OGTT) in pregnant women (Gestational diabetes):

Gestational diabetes mellitus (GDM)

Summary of the gestational diabetes mellitus work-up: 

Screening workup :

1. Perform the work-up of all pregnant ladies during the 24 to 28 weeks of gestation over the age of ≥25 years.
2. Also, check the ladies even they are  <25 years of age with the presence of the risk factor.
3. Perform mini OGTT with 50 grams of glucose without any relation to the food.
   1. Measure the glucose level at one hour.
   2. If this glucose level is ≥140 mg/dL, then perform the complete OGTT.

Diagnostic workup:

1. Perform OGTT after 8 to 14 hours of fast.
2. Take fasting glucose orally.
3. Give 100 grams of glucose.
4. Measure blood glucose hourly for 3 hours.
5. At least two values must exceed all values.
6. If results are normal in a clinically suspected case, then repeat OGTT in 3rd trimester.

 Treatment

1. The basic need is to control the diet.
2. The second important need is physical activity.
3. Can have daily glucose level and accordingly give the medication.
4. For management of GDM during pregnancy is, keep fasting blood glucose level 60 to 110 mg/dL, and postprandial level <150 mg/dL.
5. It is needed to measure urine 24-hours estriol level for the fetus viability.
6. Also, check amniotic fluid for fetal pulmonary maturity.
7. During labor keep the blood glucose level between 80 to 100 mg/dL, because there may be marked insulin sensitivity during the immediate postpartum period.
8. Evaluate the patient after 6 weeks of postpartum.

Criteria For Adequate Treatment  Is :

1. The fasting level should be around 95 mg/dL or less.
2. Postprandial, 1- hour level is around 140 mg/dL or less.
3. Postprandial, 2- hours level is 120 mg/d or less.

• Gestational diabetes mellitus goes away after pregnancy.
• In ladies with GDM, there are 2 in 3 chances to develop GDM in other pregnancies.
  • please for more information see other topics on Diabetes mellitus.