ACOG guidelines for gestational diabetes screening

Hello there! I'd be absolutely delighted to shed some light on the ACOG (American College of Obstetricians and Gynecologists) guidelines for gestational diabetes screening. It's a really important topic in prenatal care, aiming to identify and manage gestational diabetes mellitus (GDM), a condition where glucose intolerance begins or is first recognized during pregnancy. Catching it early can make a huge difference for both mom and baby! 💖

When to Screen for GDM?

For most pregnant individuals, screening typically occurs between 24 and 28 weeks of gestation. However, if someone has significant risk factors for undiagnosed type 2 diabetes or early GDM (e.g., severe obesity, history of GDM in a previous pregnancy, polycystic ovary syndrome), their healthcare provider might recommend screening earlier, even in the first trimester. If that early screen is negative, they'll usually be re-screened at the standard 24-28 week window.

The Two Main Screening Approaches

ACOG acknowledges and discusses two primary strategies for GDM screening:

1. The One-Step Strategy (75-gram Oral Glucose Tolerance Test - OGTT):

• This method involves a single, diagnostic 75-gram OGTT.
• After an overnight fast (at least 8 hours), blood glucose levels are measured at three time points: fasting, 1 hour, and 2 hours after consuming the glucose solution.
• GDM is diagnosed if any one of the following plasma glucose values are met or exceeded:
• Fasting: $\ge 92 \text{ mg/dL}$ ($\ge 5.1 \text{ mmol/L})$
• 1-hour: $\ge 180 \text{ mg/dL}$ ($\ge 10.0 \text{ mmol/L})$
• 2-hour: $\ge 153 \text{ mg/dL}$ ($\ge 8.5 \text{ mmol/L})$
• This approach is endorsed by organizations like the World Health Organization (WHO) and the International Association of Diabetes and Pregnancy Study Groups (IADPSG).

2. The Two-Step Strategy (50-gram Glucose Challenge Test followed by 100-gram OGTT):

This is the more traditional and still widely used approach in the United States, often preferred by ACOG. It starts with a screening test:

Step 1: 50-gram Glucose Challenge Test (GCT)

• You'll drink a 50-gram glucose solution, and your blood glucose will be measured 1 hour later. Fasting isn't required for this initial screen.
• If your 1-hour glucose level is:
• $\ge 130 \text{ mg/dL}$ ($\ge 7.2 \text{ mmol/L})$
• $\ge 135 \text{ mg/dL}$ ($\ge 7.5 \text{ mmol/L})$
• $\ge 140 \text{ mg/dL}$ ($\ge 7.8 \text{ mmol/L})$
• ...depending on the specific threshold chosen by your provider (140 mg/dL is most common), you'll proceed to the diagnostic 100-gram OGTT. Some providers use a lower threshold like 130 mg/dL to increase sensitivity.

Step 2: 100-gram Oral Glucose Tolerance Test (OGTT)

• This diagnostic test is performed after an overnight fast.
• Blood glucose is measured at four time points: fasting, 1 hour, 2 hours, and 3 hours after consuming the 100-gram glucose solution.
• GDM is diagnosed if at least two of the following plasma glucose values are met or exceeded (using the Carpenter-Coustan thresholds, commonly applied by ACOG):
• Fasting: $\ge 95 \text{ mg/dL}$ ($\ge 5.3 \text{ mmol/L})$
• 1-hour: $\ge 180 \text{ mg/dL}$ ($\ge 10.0 \text{ mmol/L})$
• 2-hour: $\ge 155 \text{ mg/dL}$ ($\ge 8.6 \text{ mmol/L})$
• 3-hour: $\ge 140 \text{ mg/dL}$ ($\ge 7.8 \text{ mmol/L})$
• (There's also another set of thresholds, the National Diabetes Data Group (NDDG) criteria, which are slightly different, but Carpenter-Coustan are more prevalent in current ACOG discussions.)

ACOG's Current Stance

ACOG acknowledges both the one-step and two-step approaches, recognizing that there isn't a consensus on which method is superior. They generally support the continued use of the two-step strategy, primarily due to concerns about the potential for increased diagnoses and associated interventions/costs with the one-step approach, without clear evidence of improved outcomes. Ultimately, the choice of screening method often depends on clinical judgment, patient factors, and institutional preferences. 👩‍⚕️

It's always best to discuss these options and your personal risk factors with your healthcare provider to determine the most appropriate screening plan for you. I hope this detailed breakdown helps clarify the ACOG guidelines! Let me know if you have more questions. 😊