This type is commonly referred to as diet controlled GDM or A1GDM. GDM that requires medication to achieve and maintain normal blood glucose levels is often referred to as A2GDM. Since many women aren’t screened for diabetes before pregnancy, it can be difficult to distinguish GDM from preexisting diabetes (ACOG 2018).
Who’s at risk?
Obesity and increased age increase the risk for GDM. Additionally, there is an increased prevalence of GDM among Hispanic, African American, Native American, and Asian or Pacific Islander women. Other risk factors include:
- Physical inactivity
- Cardiovascular disease
- First-degree relative with diabetes
- Previously given birth to a neonate weighing 4,000 g or more
- Previous pregnancy with GDM
- High-density lipoprotein cholesterol level less than 35 mg/dL (0.9 mmol/L)
- Triglyceride level greater than 250 mg/dL (2.82 mmol/L)
- Polycystic ovarian syndrome
- Hemoglobin A1c greater than or equal to 5
- Impaired glucose tolerance
- Impaired fasting with prior testing (ADA 2020, ACOG 2018).
Women with GDM have an increased risk for developing preeclampsia and undergoing a cesarean delivery. Moreover, women with GDM have an increased risk of developing diabetes (commonly type 2 diabetes) later in life. It’s estimated that 70% of women who experienced GDM will develop diabetes, usually 22 to 28 years later (ACOG 2018).
Neonates born to women with GDM are at increased risk of macrosomia, neonatal hypoglycemia, hyperbilirubinemia, shoulder dystocia, and birth trauma. There is also an increased risk for stillbirth (ACOG 2018).
Screening for GDM: One step or two?
According to the American Diabetes Association, GDM screening and diagnosis can be performed with either a one-step or two-step strategy. With a one-step strategy, the patient fasts overnight for at least eight hours, a clinician draws a fasting glucose level, administers a 75-g oral glucose tolerance test, and then draws blood at 1- and 2-hour intervals. The following plasma glucose levels confirm GDM using this method:
- Fasting result: 92 mg/dL (5.1 mmol/L)
- 1-hour result: 180 mg/dL (10 mmol/L)
- 2-hour result: 153 mg/dL (8.5 mmol/L) (ADA 2020)
With the two-step strategy, the clinician administers a 50-g glucose loading test (nonfasting), and then draws the patient’s blood an hour later. If the 1-hour result is 130 mg/dL (7.2 mmol/L) or greater, the clinician refers the patient for step two testing.
With step two testing, the patient fasts, the clinician draws a fasting glucose level, administers a 100-g oral glucose tolerance test, and then draws the patient’s blood at 1-, 2-, and 3-hour intervals. Using this method, the practitioner confirms GDM when at least two (or one according to the American College of Obstetricians and Gynecologists) of the patient’s plasma glucose levels meet or exceed the following levels:
- Fasting result: 95 mg/dL (5.3 mmol/L)
- 1-hour result: 180 mg/dL (10 mmol/L)
- 2-hour result: 155 mg/dL (8.6 mmol/L)
- 3-hour result: 140 mg/dL (7.8 mmol/L) (ADA 2020)
Banning together to fight GDM
Patients with GDM require the aid of a multidisciplinary team that may include an obstetrician, an endocrinologist who specializes in diabetes, a registered dietician, a diabetes educator, and a home health care nurse. Home visits for GDM may be indicated to provide and reinforce patient teaching, assess for compliance with the care plan, and monitor maternal and fetal health. Care includes:
- Dietary counseling to ensure that the patient has an individualized medical nutrition therapy program to achieve euglycemia, prevent ketosis, provide for adequate weight gain, and contribute to appropriate fetal growth and development (ADA 2020, ACOG 2018).
- Lifestyle changes that include regular moderate physical activity, as tolerated. Have the patient aim for 30 minutes of moderate-intensity aerobic exercise at least 5 days a week or a minimum of 150 minutes per week.
- Some patients may require an antidiabetic agent, such as insulin, metformin, or glyburide.
American College of Obstetricians and Gynecologists (ACOG). (2018). ACOG practice bulletin no. 190: Gestational diabetes mellitus. Obstetrics & Gynecology, 131, e49-e64.
American Diabetes Association. (2020). Standards of medical care in diabetes-2020. Diabetes Care, 43, S1–S212.