The patient's result of 156 mg/dL on the 1-hour, 50 g glucose challenge test (GCT) is considered a positive screen for gestational diabetes mellitus (GDM), as it exceeds the commonly used thresholds of 130-140 mg/dL. A positive GCT is not diagnostic but indicates the need for further testing. The standard, accepted next step in the two-step screening approach is to perform a confirmatory 3-hour, 100 g oral glucose tolerance test (OGTT). A diagnosis of GDM is made based on the results of this second test. Initiating treatment or dietary changes before a formal diagnosis is premature.

A. Repeat the 50 g oral glucose challenge: The initial screening test was positive; repeating it is redundant and delays the necessary diagnostic evaluation.

C. Advise the patient to follow an American Diabetic Association diet plan: Dietary intervention is a primary treatment for GDM, but it should only be initiated after a confirmed diagnosis from the 3-hour OGTT.

D. Begin insulin treatment: Insulin is a pharmacological treatment for GDM that is not controlled by diet and exercise. It is inappropriate without a confirmed diagnosis.

E. Order a fetal ultrasound examination: While fetal ultrasounds are important for monitoring fetal growth in pregnancies complicated by GDM, it is not the next step for diagnosing the condition.

1. American College of Obstetricians and Gynecologists (ACOG). (2018). ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstetrics & Gynecology

131(2)

e49-e64. (Reaffirmed 2021). In the section "Screening and Diagnosis

" the bulletin outlines the two-step approach

stating that a positive 50-g screen should be followed by a 3-hour 100-g OGTT for diagnosis. DOI: 10.1097/AOG.0000000000002501

2. American Diabetes Association Professional Practice Committee. (2023). 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2023. Diabetes Care

46(Suppl 1)

S254–S266. Section 15.3

"Screening for and Diagnosis of GDM

" describes the two-step strategy where a positive 1-hour 50-g screen is followed by a 3-hour 100-g OGTT. DOI: 10.2337/dc23-S015

3. Landon

M. B.

& Gabbe

S. G. (2011). Gestational diabetes mellitus. Obstetrics & Gynecology

118(6)

1379–1393. This peer-reviewed article discusses the screening protocols

explicitly stating the progression from a 50-g glucose challenge to a 100-g oral glucose tolerance test for diagnosis. DOI: 10.1097/AOG.0b013e3182364d39