As per World Health Organization, gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. GDM is classified as per the treatment modality:
- A1GDM – Diabetes managed without medication and is controlled by diet and workout
- A2GDM – Diabetes managed with medication to get adequate glycemic control
Unlike type 1 diabetes, GDM doesn’t occur because of lack of insulin but because of other hormones produced during pregnancy that make insulin less effective, leading to insulin resistance (IR). GDM symptoms disappear post-pregnancy.
What causes GDM?
GDM is related to:
- β-cells dysfunction or delayed response of β-cells to high blood glucose levels
- marked insulin resistance secondary to placental hormonal release
The placenta supplies the fetus with the required nutrition and water necessary for growth. It also produces a variety of hormones to maintain the pregnancy and to prevent any complications. But some of these hormones like estrogen, cortisol, human placental lactogen have a blocking effect on insulin which leads to IR. This is called the contra-insulin effect and begins around 20 to 24 weeks into the pregnancy.
Human placental lactogen is also known to provoke alterations and modifications in the insulin receptors that affect the insulin-mediated glucose uptake in the cells, thus leading to high blood glucose levels.
What are the risk factors?
Although any woman can develop GDM, certain risk factors increase the chances of getting GDM:
- Overweight or obesity (BMI>25)
- Sudden gain of weight during pregnancy
- Family history of diabetes
- History of giving birth to an infant weighing greater than 9 pounds
- Ethnicity
- Prediabetes
- Sedentary lifestyle
- High triglycerides level (>250)
- Polycystic ovary syndrome
Diagnostic Tests
Pregnant females having high-risk factors or showing symptoms of increased thirst, hunger or urination, are screened for GDM at 24 to 28 weeks of pregnancy with a 50-g, 1-h oral glucose challenge test. If,
- Values ≥ 140 mg/dL,
the confirmatory test is done with a 100-g, 3-hour oral glucose tolerance test, and blood is drawn every 1 hour for the next 3 hours. The presence of two or more abnormal values establishes GDM,
- 1 st hour > 180 mg/ dL
- 2 nd hour > 155 mg/ dL
- 3 rd hour > 140 mg/ dL
ACOG (The American College of Obstetricians and Gynecologists) recommends following values as normal for blood glucose levels in pregnancy
- Fasting < 95 mg/ dL
- 1-hour postprandial between 130-140 mg/ dL
- 2-hour postprandial < 120 mg/ dL
Complications of GDM
GDM occurs too late in the pregnancy, so it doesn’t cause any birth effects and all the complications of GDM are manageable and preventable. There are 2 types of complications: maternal and fetal
-
Maternal Complications
- High risk of type 2 diabetes later in life
- High risk of cesarean delivery
- Pre-eclampsia – the onset of high blood pressure and a high amount of protein in the urine
-
Fetal Complications
- Macrosomia – Baby is considerably larger than normal. Maternal blood having high blood glucose levels activates the fetal pancreas to release more insulin, this insulin starts using glucose for fetal development and starts storing excess glucose as fat in the fetal body. This results in increased size of the baby
-
Hypoglycemia – Low blood sugar levels in babies immediately after delivery. The fetus has high insulin levels because of the mother’s GDM. After delivery, the baby continues to have high insulin levels but no longer has high level of sugar in the blood, resulting in low blood sugar levels after delivery
Treatment and Management
GDM begins with lifestyle modification initially by diet modification, active lifestyle. The American diabetes association recommends nutritional counseling under expert guidance and not to go on a calorie deficit to lose weight because that will affect the nutrition of the baby.
The amount of exercise recommended is 30 minutes of moderate-intensity aerobic exercises at least 5 days a week.
If altering the lifestyle doesn’t lead to adequate glycemic control, it is recommended to begin pharmacologic treatment i.e. insulin injections under the physician guidance.
References:
- Johns Hopkins Medicine (2019). Gestational Diabetes Mellitus (GDM). [online] JOHNS HOPKINS Medicine
- Mirghani Dirar, A. and Doupis, J. (2017). Gestational diabetes from A to Z. World Journal of Diabetes, [online] 8(12), pp.489–511
- Quintanilla, B.S. and Heba Mahdy (2019). Gestational Diabetes. [online] Nih.gov
