What is the appropriate evaluation and management for a pregnant woman with elevated fasting plasma glucose?

Fasting Glucose of 118 mg/dL in Pregnancy

A fasting plasma glucose of 118 mg/dL in pregnancy indicates gestational diabetes mellitus (GDM) and requires immediate initiation of management with medical nutrition therapy, self-monitoring of blood glucose, and insulin therapy if glycemic targets are not achieved within 1-2 weeks.

Diagnostic Confirmation

Your patient's fasting glucose of 118 mg/dL exceeds the diagnostic threshold for GDM, which is ≥92 mg/dL (5.1 mmol/L) according to current international consensus criteria 1, 2. This single elevated fasting value is sufficient to diagnose GDM without requiring a full oral glucose tolerance test (OGTT), as the American College of Obstetricians and Gynecologists (ACOG) now accepts that one elevated value can establish the diagnosis 1, 2.

• No additional OGTT is needed when the fasting glucose already meets diagnostic criteria 2, 3
• This value falls into the category requiring treatment, as it exceeds 105 mg/dL (5.8 mmol/L), which is associated with increased surveillance needs for fetal complications 1

Immediate Management Steps

1. Initiate Medical Nutrition Therapy and Lifestyle Modifications

Begin nutritional counseling immediately as the cornerstone of GDM management 4, 5. All women with GDM should receive instruction on:

• Carbohydrate-controlled diet with at least 150 g carbohydrate per day distributed throughout the day 1
• Moderate-intensity physical activity unless obstetric contraindications exist 1, 4
• Weight management appropriate for gestational age 4, 5

2. Implement Daily Self-Monitoring of Blood Glucose

Prescribe a glucometer and instruct the patient to check blood glucose daily at the following times 1:

• Fasting glucose upon waking
• 1-hour postprandial after each main meal (superior to preprandial monitoring for insulin-treated patients) 1

Target glycemic goals are 1:

• Fasting: <95 mg/dL (5.3 mmol/L)
• 1-hour postprandial: <140 mg/dL (7.8 mmol/L)
• 2-hour postprandial: <130 mg/dL (7.2 mmol/L)

3. Plan for Insulin Therapy

Given that your patient's fasting glucose of 118 mg/dL significantly exceeds the treatment threshold of 105 mg/dL, anticipate that insulin therapy will likely be required 1. Insulin should be initiated as first-line pharmacologic therapy if:

• Medical nutrition therapy fails to maintain fasting glucose <95 mg/dL within 1-2 weeks 1, 4, 5
• Postprandial targets are not achieved 1

Insulin is the preferred agent over oral hypoglycemic agents, which are not FDA-approved for GDM treatment 1, 6.

Maternal and Fetal Surveillance

Maternal Monitoring

Increase surveillance for maternal complications given the elevated fasting glucose 1:

• Blood pressure monitoring at each visit to detect hypertensive disorders 1
• Urine protein assessment for preeclampsia screening 1
• Do not use urine glucose monitoring, as it is not useful in GDM 1
• Consider urine ketone monitoring if caloric restriction is implemented 1

Fetal Monitoring

Enhanced fetal surveillance is mandatory when fasting glucose exceeds 105 mg/dL 1:

• Serial ultrasound examinations to assess fetal growth and detect macrosomia 4, 5
• Measurement of fetal abdominal circumference in early third trimester to identify infants at risk for macrosomia 1
• Increased surveillance for fetal demise, particularly if pregnancy progresses past term 1
• Regular obstetric examinations including ultrasound 4, 5

Delivery Planning

Plan for delivery at 38 completed weeks of gestation unless obstetric considerations dictate otherwise 1. Key points:

• GDM alone is not an indication for cesarean delivery 1
• GDM alone is not an indication for delivery before 38 weeks 1
• Prolongation past 38 weeks increases macrosomia risk without reducing cesarean rates 1

Postpartum Management

Immediate Postpartum (4-12 weeks)

All women with GDM must undergo reclassification of glucose tolerance using a 75-g OGTT at 4-12 weeks postpartum 1, 4, 5. Use standard non-pregnancy diagnostic criteria:

• Fasting ≥126 mg/dL indicates diabetes 1
• 2-hour glucose ≥200 mg/dL indicates diabetes 1
• Values between these thresholds indicate prediabetes 1

Long-term Follow-up

Counsel the patient about significantly elevated lifetime diabetes risk 1:

• Women with GDM have a 3.4-fold increased risk of developing type 2 diabetes 2
• Lifelong screening for diabetes or prediabetes is required at least every 3 years 1, 7
• Preventive measures include weight management, healthy diet, and regular physical activity 4, 5
• Offspring are at increased risk for obesity and glucose intolerance in adolescence and young adulthood 1

Neonatal Care

Coordinate with pediatrics for neonatal glucose monitoring immediately after delivery 4, 5:

• Neonates are at high risk for hypoglycemia and require blood glucose measurements after birth 1, 4, 5
• Appropriate intervention should be initiated if hypoglycemia is detected 4, 5
• Encourage breastfeeding 1

Common Pitfalls to Avoid

• Do not delay treatment while waiting for a formal OGTT when fasting glucose already meets diagnostic criteria 2, 3
• Do not rely on HbA1c alone for diagnosis or monitoring in pregnancy, as it has poor sensitivity for detecting GDM 1, 8
• Do not use oral hypoglycemic agents as first-line therapy, as they are not FDA-approved for GDM 1
• Do not forget postpartum OGTT, as this is critical for identifying persistent diabetes and preventing future complications 1, 7, 4
• Do not perform OGTT in patients with history of bariatric surgery due to risk of postprandial hypoglycemia 4, 5