Screening & Diagnosis for Gestational Diabetes

Screening & Diagnosis for Gestational Diabetes

WHEN SHOULD I BE TESTED?

In women without prior diabetes and at low-risk, screening for gestational diabetes mellitus (GDM) should be done between 24 and 28 weeks of pregnancy.1,2 

WHO SHOULD BE TESTED EARLY?

In women at higher risk, early screening for abnormal glucose metabolism is generally recommended before 15 weeks of pregnancy.1 Women with a history of GDM, obesity (body mass index >30 kg/m2), or known impaired glucose metabolism are considered to be at higher risk.3 A fasting glucose level of >110 mg/dL or an A1C level of >5.9% places women at higher risk of a later GDM and other medical risks for both the mother and the fetus.

WHAT ARE THE TESTING METHODS?

There are generally two accepted and recommended diagnostic approaches for GDM.1,2 Both are forms of oral glucose tolerance test (OGTT).

“1-Step” OGTT

Women will be asked to fast overnight for at least 8 hours before taking the test. First, the health care professional will draw blood to measure the fasting glucose levels. Then a 75 g oral glucose drink will be given, and blood draws will be taken again after 1 hour and 2 hours after the drink. GDM is diagnosed when any one of the following measurements meet and exceed the target value:

  • Fasting: 92 mg/dL
  • 1 Hour: 180 mg/dL
  • 2 Hour: 153 mg/dL

 

“2-Step” OGTT

First Step. No fasting is required for the first step. A 50 g oral glucose drink will be given, and blood draw will be taken after 1 hour. If glucose levels measures >130 mg/dL, then women will have to come back for the second step. 

Second Step. Women will be asked to fast overnight for at least 8 hours before taking the test. First, the health care professional will draw blood to measure the fasting glucose levels. Then a 100 g oral glucose drink will be given, and blood draws will be taken again after 1 hour, 2 hours, and 3 hours after the drink. GDM is diagnosed when any one of the following measurements meet and exceed the target value:

  • Fasting: 95 mg/dL
  • 1 Hour: 180 mg/dL
  • 2 Hour: 155 mg/dL
  • 3 Hour: 140 mg/dL

Can I Get a Normal Blood Test?

Although getting a simple blood draw (without fasting or needing to drink oral glucose) can measure A1C levels, this method is currently not recommended for screening GDM as changes to hemoglobin levels and red blood cell turnover in pregnancy can result in inaccurate results.1

 

References:
1. ElSayed NA, Aleppo G, Aroda VR, et al. 2. Classification and Diagnosis of Diabetes: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S19-S40. doi:10.2337/dc23-S002
2. US Preventive Services Task Force. Screening for Gestational Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(6):531-538. doi:10.1001/jama.2021.11922
3. Randel A. ACOG Releases Guideline on Gestational Diabetes. Am Fam Physician. 2014;90(6):416-417.

  

(Disclaimer)

The content of this article is intended to provide a general information and knowledge on the subject matter. The views expressed in newsletters, articles, and blogs in the i-SENS USA website are not necessarily those of i-SENS Incorporated, i-SENS USA Incorporated or our publishers. Medical or nutritional information on i-SENS USA website is not intended to replace professional medical advice – you should always consult a specialist with any questions about your specific circumstances.

 

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