Diabetes Mellitus:- Part 4 – Gestational Diabetes Mellitus, Oral glucose tolerance test, (OGTT)
Gestational Diabetes Mellitus
- 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.
- It is better to give glucose in 7-up, where it will be well tolerated.
- Collect fasting blood and then collect blood samples at 30, 60, 90, and 120 minutes.
- Multiple samples are taken at half-hour intervals along with the urine sample.
- In pregnant ladies, collect blood at 60, 120, and 180 min after glucose.
- Sometimes the sample is taken at 1, 2, 3, and up to 4 hours.
Purpose of the test (Indications)
- To confirm the diagnosis of gestational diabetes.
- It is used to diagnose Diabetes mellitus.
- It is also used to evaluate hypoglycemia.
- Patient with family H/o diabetes.
- Patients with obesity.
- Patients with H/O recurrent infection.
- Patients with H/O delayed wound healing.
- Ladies with H/O stillbirths or delivering obese babies.
- Patients with H/O random glycosuria or hyperglycemia during pregnancy or after myocardial infarction, surgery, or stress.
Precautions for Gestational Diabetes Mellitus
- Advice to the patient to take >150 grams of the carbohydrates in the diet in the last 3 days before the test.
- Stop these drugs at least 3 days before the test hormone, contraceptives, steroids, salicylates, and anti-inflammatory drugs.
- Stop diuretics, hypoglycemic agents, antihypertensive drugs, and anticonvulsants.
- Stress can increase glucose level.
- If the patient does not tolerate the glucose and vomits out, that may give a false result.
- Avoid glucose tolerance tests in the following conditions:
- If there is persistent fasting hyperglycemia >140 mg/dL (>7.8 mmol/L).
- In case if there is a normal fasting glucose level.
- Patient with known diabetes mellitus.
- In case if two hours glucose >200 mg/dL (>11.1 mmol/L).
Indications for the diagnosis of Gestation Diabetes Mellitus
- This is recommended that screening should be done on all pregnant women between 24 and 28 weeks of gestation.
- This should be advised for women aged 25 years or older.
- Also advised before the age of 25 years if the women are obese or there is a family history of DM.
Pathophysiology of Gestational Diabetes Mellitus
- Gestational diabetes mellitus is defined as any degree of glucose intolerance which is seen during pregnancy.
- Usually seen around 24 weeks of gestation.
- GDM can also be defined as hyperglycemia that develops for the first time during pregnancy. This may be seen in 4% of pregnant ladies.
- A normal pregnancy is associated with increased insulin resistance, especially in the late second and third trimesters.
- This will occur in those pregnant ladies who can not maintain a sufficient insulin level.
- The risk factors are:
- Family history of a first-degree relative with diabetes mellitus.
- In obese ladies.
- In the case of late maternal age, usually after the age of 40 years.
- If there is glycosuria.
- Bad previous delivery history like stillbirth and macrosomia.
- Screening should be performed between 24 to 28 weeks of gestation.
- 3% to8% of pregnant women have gestational diabetes.
Complications of gestational diabetes mellitus:
- The detection of early GDM will reduce the risk of prenatal fatal outcomes like:
- Excessive fetal growth.
- Birth trauma.
- Fetal morbidity.
Screening gestational diabetes mellitus(GDM) during pregnancy:
- It can be assessed by a one-hour blood glucose level if it is >140 mg/dL. Then advise OGTT for three hours.
- O’Sullivan test is one-hour glucose after 50 grams of oral glucose intake.
- Screening for GDM advises OGTT with 50 grams of glucose.
- Check the one-hour glucose level, which is called the O’Sullivan test.
- Screening should be done between 24 to 28 weeks of gestation.
- If one hour sample is >140 mg/dL, then taking a 3-hour 100-grams of glucose(OGTT) is necessary.
- Normal pregnancy is associated with increased insulin resistance, especially in the second and third trimesters.
Screening of gestational diabetes mellitus during the postpartum period:
- If the results are abnormal during pregnancy, then take OGTT postpartum.
- If postpartum OGTT is normal, then label diabetes mellitus during pregnancy.
- Check blood glucose on every visit because of the increased risk of diabetes mellitus, which is 30% during the next 5 to 10 years.
- 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%.
- Another possibility is a clear-cut case of diabetes mellitus, which can occur in 10% of the cases.
- The rest of the ladies are normal, and they may develop diabetes mellitus in the next 5 to 10 years.
Risk factors for Gestational Diabetes Mellitus include:
- A family history of diabetes in first-degree relatives.
- Advanced maternal age.
- A selected bad outcome in the last pregnancy, like stillbirth or macrosomia.
Modified criteria for the diagnosis of GDM include:
- Low-risk patients are:
- Below the age of 25 years.
- Normal weight before the pregnancy.
- The ethnic group with a low incidence of GDM.
- No known first-degree relative with diabetes mellitus.
- No history of poor obstetric outcomes.
- There is no history of abnormal glucose tolerance.
- Average-risk patients are:
- All those patients fall between low and high-risk patients.
- They should be tested between 24 to 28 weeks of gestation.
- High-risk patients are:
- Marked obesity.
- History of GDM.
- Strong family history of diabetes mellitus.
Important facts for Gestational diabetes mellitus (GDM):
- OGTT is not recommended to see the complications of Diabetes mellitus.
- Its use is also discouraged for fasting hypoglycemia.
- In non-pregnant ladies and children, the OGTT is not recommended as a screening test.
- For a pregnant lady, 50 G glucose is recommended for screening.
- The serum glucose level of >150 mg/dl at 1 hour is considered for further testing.
- There is a rapid response of insulin to oral glucose, and the peak is 30 and 60 minutes.
- Glucose comes to normal in 3 hours.
- Glucose will not appear in the urine in a normal pattern.
Procedure for Oral glucose tolerance test (OGTT):
- Record patient weight.
- 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.
- Pregnant ladies can be given 100 grams.
- Can perform the test on pregnant ladies with 50 grams of glucose.
- Non-pregnant ladies can be given 75 grams.
- Take the fasting blood for fasting glucose levels.
- Give glucose (Glaxo’s-D) 75 to 100 grams in 5 minutes.
- Pregnant ladies can perform the test with 50 grams of glucose.
- Now take the blood 30, 60, and 90. 120 and 180 minutes (some books recommend 30, one hour, 2 hours, and 3 hours) after glucose intake.
- To check the hypoglycemia, advise 4 hours sample.
- Also, take the urine sample with every blood sample.
Procedure for collection of the blood and urine during OGTT:
|When to take a sample||Blood sample to be taken||A urine sample is taken||Some recommend|
|4 hours||Yes, to check hypoglycemia|
Normal values of glucose
- NORMAL WHEN
- Fasting glucose = < 110 mg/dl.
- Random glucose = < 140 mg/dl.
- 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 samples are negative.
- >60 years fasting = 70 to 115 mg/dL
Gestational diabetes normal one hour = <140 mg/dL
- Diabetes Mellitus when:
- Fasting glucose = 126 mg/dl or above
- Postprandial glucose = 200 mg/dl or above
- Random glucose more than 200 mg/dl with H/o polyuria, polydipsia, ketonuria, and weight loss.
- IMPAIRED GLUCOSE when:
- Impaired fasting Glucose = 110 to <126 mg/dl
- Impaired glucose tolerance = 140 to <200 mg/dl
|Diagnosis||Fasting glucose level||Random glucose level||2-hour glucose level (in OGTT)||HbA1c|
|Prediabetics||100 to 125 mg/dL||140 to 199 mg/dL||140 to 199 mg/dL||5.7 to 6.4%|
|Diabetes mellitus||> 126 mg/dL||>200 mg/dL||>200 mg/dL||>6.5%|
Normal values of OGTT in Adults:
|Time||Glucose value||Urine glucose|
|Fasting||<110 mg/dL or 6.1 mmol/L (70 to 105 mg/dl)||negative|
|30 min||110 to 170 mg/dL ( 11.1 mmol/L)||negative|
|one hour||120 to 170 mg/dL (11.1 mmol/L)||negative|
|2 hours||<140 mg/dL or 7.8 mmol/L (70 to 120 mg/dL)||negative|
|3 hours||70 to 115 mg/dL or <6.4 mmol/L||negative|
|4 hours||70 to 115 mg/dL or <6.4 mmol/L||negative|
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.
|Time||mg/dl in plasma/serum||Urine sugar||mg/dL in whole blood|
At least two values must meet or exceed the following values for GDM based on the oral glucose tolerance test:
|Timings||75 grams overload mg/dL||100 grams overload mg/dL|
Criteria for the positive 100 grams (OGTT) in pregnant women (Gestational diabetes):
|Time of the blood taken||Glucose level mg/dL|
Summary of the gestational diabetes mellitus work-up:
Screening workup :
- Perform the work-up of all pregnant ladies during the 24 to 28 weeks of gestation over the age of ≥25 years.
- Also, check the ladies even if they are <25 years of age with the risk factor.
- Perform mini OGTT with 50 grams of glucose without any relation to the food.
- Measure the glucose level for one hour.
- If this glucose level is ≥140 mg/dL, then perform the complete OGTT.
Diagnostic workup for Gestation diabetes mellitus:
- Perform OGTT after 8 to 14 hours of fasting.
- Take fasting glucose orally.
- Give 100 grams of glucose.
- Measure blood glucose hourly for 3 hours.
- At least two values must exceed all values.
- If results are normal in a clinically suspected case, then repeat OGTT in 3rd trimester.
Treatment of Gestation diabetes mellitus:
- The basic need is to control the diet.
- The second important need is physical activity.
- Can have daily glucose level and accordingly give the medication.
- For management of GDM during pregnancy, keep fasting blood glucose level 60 to 110 mg/dL and postprandial level <150 mg/dL.
- It is needed to measure urine 24-hours estriol level for the fetus viability.
- Also, check amniotic fluid for fetal pulmonary maturity.
- 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.
- Evaluate the patient after 6 weeks of postpartum.
Criteria For Adequate Treatment Are:
- The fasting level should be around 95 mg/dL or less.
- Postprandial, 1- hour level is around 140 mg/dL or less.
- The 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.