What is the recommended treatment for a pregnant woman diagnosed with gestational diabetes after 24–28 weeks?

Treatment for Gestational Diabetes

Begin lifestyle intervention immediately upon diagnosis at 24-28 weeks, and add insulin therapy if glycemic targets are not achieved within 1-2 weeks of dietary modification and exercise. 1

Initial Management: Lifestyle Intervention First-Line

Lifestyle modification is the cornerstone and essential first-line treatment for all women diagnosed with gestational diabetes. 2, 1 This includes:

• Medical nutrition therapy with calorie restriction and low glycemic index diet to avoid postprandial hyperglycemia and reduce insulin resistance 3, 4
• Daily physical exercise as part of the comprehensive lifestyle approach 3, 4
• Self-monitoring of blood glucose to assess response to conservative management 4

Approximately 70-85% of women with GDM can achieve adequate glycemic control with lifestyle modifications alone, meaning the majority will not require pharmacologic therapy. 1

Glycemic Targets to Achieve

Target the following capillary blood glucose thresholds to determine if pharmacologic therapy is needed: 1

• Fasting plasma glucose <95 mg/dL (5.3 mmol/L) 1
• 1-hour postprandial <140 mg/dL (7.8 mmol/L) 1
• 2-hour postprandial <120 mg/dL (6.4 mmol/L) 1

These targets align with NICE guidelines and should be maintained without causing hypoglycemia. 2

When to Escalate to Pharmacologic Therapy

Add pharmacologic treatment if lifestyle modifications fail to achieve target glucose levels after 1-2 weeks of dietary and exercise interventions. 2, 1, 4

The majority of randomized controlled trials (87%) use very tight criteria for starting medications: either 1 or 2 blood glucose values exceeding target thresholds over a 1-2 week period. 5 Specifically:

• If 1-2 fasting values ≥90-95 mg/dL over 1-2 weeks 5
• If 1-2 postprandial values ≥120 mg/dL (2-hour) over 1-2 weeks 5

Pharmacologic Treatment Options

Insulin: First-Line Medication

Insulin is the preferred and gold standard pharmacologic treatment for gestational diabetes during pregnancy. 2, 1, 3, 4 The Chinese guidelines explicitly advise against oral hypoglycemic agents during pregnancy due to lacking long-term safety data. 2

Metformin: Alternative When Insulin Cannot Be Used

Metformin can serve as an alternative treatment when insulin cannot be prescribed, though it is not equal to insulin in effectiveness. 3, 4 Key considerations:

• Short-term safety data for metformin are reassuring, and some countries consider it first-line treatment 3
• Up to 46% of women on metformin may require additional insulin to maintain target glucose levels 4
• Long-term effects on offspring require further investigation 3

Glyburide: Use Only When Benefits Outweigh Risks

Glyburide should be used only when benefits surpass possible risks, as safety concerns have been raised regarding its use during pregnancy. 3

Fetal Surveillance and Monitoring

Perform ultrasound surveillance to assess fetal abdominal circumference, as measurements exceeding the 75th percentile for gestational age may indicate the need for more intensive glycemic control. 1

For women requiring medications or with poor glucose control, fetal surveillance should start at 32 weeks of gestation. 6

Critical Clinical Pitfall to Avoid

Monitor for a rapid reduction in insulin requirements later in pregnancy, as this can indicate placental insufficiency requiring prompt evaluation. 1 This is a red flag that should not be missed.

Delivery Planning

For well-controlled GDM (diet-controlled), continue pregnancy to term (39-40 weeks) with regular monitoring. 1, 6 Women with diet-controlled GDM can wait for spontaneous labor expectantly if there are no obstetric indications for birth. 4

For suboptimal glycemic control despite maximal therapy or those requiring insulin, consider earlier delivery at 39 0/7 to 39 6/7 weeks of gestation. 1, 6 Elective induction at term is recommended by authorities for women with GDM under insulin therapy. 4

Assess for fetal macrosomia (estimated fetal weight >4,000 g) and discuss risks/benefits of prelabor cesarean delivery if estimated fetal weight exceeds 4,500 g. 6

Postpartum Follow-Up

Screen for persistent diabetes at 4-12 weeks postpartum using a 75g oral glucose tolerance test with non-pregnancy diagnostic criteria. 2, 1, 7

Counsel about lifelong screening for diabetes or prediabetes at least every 3 years, as women with GDM have a 3.4-fold increased risk of developing type 2 diabetes. 1, 7 Women found to have prediabetes should receive intensive lifestyle interventions and/or metformin to prevent progression to diabetes. 2, 7

Encourage breastfeeding and continued lifestyle modifications, as these can reduce the long-term risk of developing overt diabetes. 6, 8