Screening and Referral
GDM: Referral to an RDN
➤ Pregnant women who are diagnosed with GDM should be referred to a
registered dietitian nutritionist (RDN) for medical nutrition therapy (MNT).
Individualized MNT is important in helping pregnant women with GDM
achieve and maintain normal glycemic levels and appropriate weight
gain, while meeting essential nutrients for pregnancy to promote positive
maternal and fetal outcomes. (Strong, Imperative)
➤ According to the American Diabetes Association (ADA), "Gestational diabetes
mellitus (GDM) is diabetes diagnosed in the second or third trimester of
pregnancy that is not clearly either type 1 or type 2 diabetes (ADA, 2016)."
➤ All pregnant women are generally tested for GDM between 24–28 weeks of
gestation, [American College of Obstetricians and Gynecologists (ACOG),
2013] if they have not previously been diagnosed with overt diabetes.
➤ Screening and diagnosis of GDM may be made by one of two strategies at
24–28 weeks of gestation:
ONE-STEP STRATEGY:
• Perform a 75g oral glucose tolerance test (OGTT), with plasma glucose measurement
when patient is fasting and at 1 and 2 hours. The OGTT should be performed in the
morning after an overnight fast of at least 8 hours. A GDM diagnosis is made when
any of the following plasma glucose values are met or exceeded:
Time Criteria
Fasting 92 mg/dL (5.1 mmol/L)
1 h 180 mg/dL (10.0 mmol/L)
2 h 153 mg/dL (8.5 mmol/L)
TWO-STEP STRATEGY
• Step 1: Perform a 50g glucose load test (GLT) (nonfasting), with plasma glucose
measurement at 1 hour. If the plasma glucose level measured 1 hour after the load
is ≥140 mg/dL (7.8 mmol/L), proceed to a 100g OGTT.
[Note: The ACOG recommends 135mg/dL (7.5mmol/L) in high-risk ethnic populations
with higher prevalence of GDM. Some experts also recommend 130mg/dL (7.2 mmol/L).]
• Step 2: The 100g OGTT should be performed when the patient is fasting.
A GDM diagnosis is made if at least two of the following four plasma glucose levels
(measured fasting and 1 h, 2 h, 3 h after the OGTT) are met or exceeded:
Time Carpenter/Coustan
National Diabetes
Data Group
Fasting 95 mg/dL (5.3 mmol/L) OR 105 mg/dL (5.8 mmol/L)
1 h 180 mg/dL (10.0 mmol/L) OR 190 mg/dL (10.6 mmol/L)
2 h 155 mg/dL (8.6 mmol/L) OR 165 mg/dL (9.2 mmol/L)
3 h 140 mg/dL (7.8 mmol/L) OR 145 mg/dL (8.0 mmol/L)
