What are the treatment guidelines for gestational diabetes?

Gestational Diabetes Treatment Guidelines

Start all women with gestational diabetes on medical nutrition therapy and self-monitoring of blood glucose immediately upon diagnosis, targeting fasting glucose <95 mg/dL, 1-hour postprandial <140 mg/dL, or 2-hour postprandial <120 mg/dL; if these targets are not achieved within 1-2 weeks despite optimal adherence to lifestyle modifications, initiate insulin therapy as the first-line pharmacologic agent. 1, 2

Initial Management: Lifestyle Modifications

Medical Nutrition Therapy

• Refer to a registered dietitian familiar with GDM management within the first week of diagnosis to develop an individualized nutrition plan 2
• The diet must provide minimum 175 g carbohydrate daily, 71 g protein daily, and 28 g fiber daily 1
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 1, 2
• Calorie intake should promote appropriate gestational weight gain according to 2009 National Academy of Medicine recommendations, with no evidence that GDM requires different calorie needs than non-GDM pregnancy 1
• Avoid hypocaloric diets (<1,200 calories/day) as they cause ketonemia and ketonuria, which are associated with lower intelligence scores in offspring 1

Physical Activity

• Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week 2
• Exercise interventions improve glucose outcomes and reduce insulin requirements, with effective regimens ranging from 20-50 minutes/day, 2-7 days/week of moderate intensity 1
• A minimum of three exercise episodes per week, each >15 minutes, is required to modify maternal glucose levels, with 2-4 weeks of regular exercise needed before glycemic improvement is observed 1

Blood Glucose Monitoring

• Check fasting glucose daily upon waking and postprandial glucose (1 or 2 hours) after each main meal 2
• Perform 4-6 daily measurements (fasting and 1-2 hours postprandial) to guide insulin dose adjustments 3
• Do not rely on HbA1c for GDM monitoring, as altered red blood cell turnover during pregnancy makes it unreliable 3

When to Initiate Pharmacologic Therapy

70-85% of women diagnosed with GDM under Carpenter-Coustan criteria can achieve control with lifestyle modifications alone 1

Indications for Insulin Initiation

• After 1-2 weeks of optimal medical nutrition therapy adherence if fasting glucose ≥95 mg/dL 3, 2
• If 1-hour postprandial glucose ≥140 mg/dL or 2-hour postprandial glucose ≥120 mg/dL 3, 2
• If signs of excessive fetal growth are observed on ultrasound 3

Pharmacologic Management

Insulin: First-Line Agent

Insulin is the preferred and recommended first-line pharmacologic agent because it does not cross the placenta to a measurable extent 1, 2

Insulin Regimen

• Begin with a basal-bolus approach distributing 40% of total daily dose as basal insulin and 60% as prandial insulin 3
• Adjust doses based on self-monitored blood glucose patterns 3
• No specific insulin regimen has demonstrated superiority in GDM, but the basal-bolus approach provides a structured starting point 3

Critical Pitfall to Avoid

Do not delay insulin initiation when glycemic targets are consistently missed despite optimal medical nutrition therapy adherence 3

Why Not Oral Agents as First-Line?

Metformin: Not Recommended First-Line

• Metformin and glyburide are not recommended as first-line treatment because they cross the placenta and long-term safety data for offspring is concerning 1, 2
• Metformin readily crosses the placenta, resulting in umbilical cord blood levels as high or higher than maternal levels 1
• In the MiG TOFU study, 9-year-old offspring exposed to metformin had higher BMI, increased waist-to-height ratio, and increased waist circumference compared to insulin-exposed offspring 1
• Follow-up studies at ages 4-10 years showed offspring exposed to metformin had higher BMI, increased obesity, and borderline increase in fat mass 1
• Metformin was associated with lower risk of neonatal hypoglycemia and less maternal weight gain than insulin, but these short-term benefits are outweighed by concerning long-term offspring outcomes 1

Sulfonylureas (Glyburide): Not Recommended First-Line

• Sulfonylureas cross the placenta with umbilical cord plasma concentrations approximately 50-70% of maternal levels 1
• Associated with increased neonatal hypoglycemia 1
• Meta-analyses show no benefit in preventing GDM, and there is no evidence-based need to continue sulfonylureas in pregnancy 1

When Oral Agents May Be Considered

There are some women with GDM requiring medical therapy who may not be able to use insulin safely 1—in these specific circumstances, metformin or glyburide may be considered as second-line options after thorough counseling about placental transfer and offspring safety concerns 1, 2

Fetal Surveillance

• Perform ultrasound assessment of fetal growth every 2-4 weeks starting in the second trimester to detect excessive growth requiring therapy intensification 3
• For women with poor glucose control or requiring medications, fetal surveillance is suggested starting at 32 weeks of gestation 4

Labor and Delivery Management

• Switch to intravenous insulin infusion during labor or cesarean section for women requiring insulin 3
• Stop all insulin immediately after delivery and monitor blood glucose before and 2 hours after meals for 48 hours 3
• Insulin resistance typically resolves after delivery 4

Postpartum Follow-Up

Women with a history of GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years 2

• Test for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g OGTT with non-pregnancy diagnostic criteria 2
• Reassess glucose parameters (fasting glucose, random glucose, HbA1c, or optimally OGTT) every 2-3 years if normal glucose tolerance is found 5
• Counsel about increased risk of type 2 diabetes and cardiovascular disease 5
• Recommend continued lifestyle modifications, breastfeeding, and consider metformin to reduce risk of progression to type 2 diabetes 4

Telehealth Option

Telehealth visits for pregnant women with GDM improve outcomes compared with standard in-person care, with demonstrated reductions in cesarean delivery, neonatal hypoglycemia, macrosomia, pregnancy-induced hypertension, preeclampsia, and preterm birth 1