Management of Gestational Diabetes Mellitus
Initial Approach: Lifestyle Modifications First
All women with gestational diabetes mellitus (GDM) should begin treatment with lifestyle modifications, including medical nutrition therapy and physical activity, with 70-85% achieving adequate glycemic control without medications 1.
Medical Nutrition Therapy
Every woman with GDM must work with a registered dietitian nutritionist to develop an individualized nutrition plan that provides adequate calories for fetal and maternal health while achieving glycemic targets 2, 3.
Minimum daily nutritional requirements include:
Carbohydrate distribution is critical: Spread carbohydrates across three small-to-moderate meals and two-to-four snacks throughout the day to minimize postprandial glucose excursions 2.
The type and amount of carbohydrate directly impacts glucose levels, particularly after meals 1, 4.
Physical Activity
Women should engage in at least 150 minutes of moderate-intensity aerobic activity per week, preferably distributed throughout the week 2, 3.
Exercise interventions have demonstrated improvements in glycemic outcomes and reductions in the need for insulin initiation 3.
Glycemic Targets for Monitoring
Self-monitoring of blood glucose in fasting and postprandial states is essential to achieve and maintain glycemic control 3.
Target Blood Glucose Levels
Postprandial monitoring is associated with better glycemic control and lower risk of preeclampsia compared to preprandial monitoring alone 1, 3.
Pharmacologic Therapy: When Lifestyle Modifications Fail
Insulin as First-Line Medication
Insulin is the preferred and recommended first-line medication for treating hyperglycemia in GDM when lifestyle modifications are insufficient 1, 2, 3.
Why Insulin is Preferred
Insulin does not cross the placenta to a measurable extent, making it the safest option for the fetus 1, 2, 3.
Treatment of GDM with lifestyle modifications and insulin has been demonstrated to improve perinatal outcomes in large randomized studies 1.
Insulin Dosing
Initial total daily insulin dose should be calculated as 0.7-1.0 units/kg of current weight 2.
Distribute as 40% basal insulin and 60% prandial insulin 2.
Insulin requirements increase exponentially during the second and early third trimesters due to physiological insulin resistance 1.
Oral Agents: Not Recommended as First-Line
Metformin and glyburide should NOT be used as first-line agents because both cross the placenta to the fetus and lack long-term safety data 1, 2, 3.
Glyburide (Sulfonylureas)
Glyburide concentrations in umbilical cord plasma reach approximately 70% of maternal levels 1.
Glyburide is associated with higher rates of neonatal hypoglycemia and macrosomia compared to insulin or metformin 1.
Glyburide failed to achieve adequate glycemic control in 23% of women with GDM in randomized controlled trials 1.
Long-term safety data for offspring are not available 1.
Metformin
Metformin crosses the placenta but was associated with lower risk of neonatal hypoglycemia and less maternal weight gain than insulin in follow-up studies 1.
Metformin failed to provide adequate glycemic control in 25-28% of women with GDM 1.
Further study of long-term outcomes in offspring is needed 1.
In some countries, metformin is considered as first-line treatment, but this is not the standard recommendation in the United States 5.
Team-Based Care and Monitoring
Team-based care through specialized centers or interprofessional team members improves outcomes 2.
Telehealth visits for pregnant women with GDM improve outcomes compared with standard in-person care 2.
Prevention of Preeclampsia
Women with type 1 or type 2 diabetes (and by extension, those at high risk with GDM) should be prescribed low-dose aspirin 60-150 mg/day (usual dose 81 mg/day) from the end of the first trimester until delivery to lower the risk of preeclampsia 1.
Critical Pitfalls to Avoid
Do NOT delay insulin initiation in women with poor glycemic control on lifestyle modifications alone 2. Early pharmacologic intervention is essential to prevent complications.
Do NOT rely solely on HbA1c for monitoring, as it represents an average and may not capture physiologically relevant glycemic parameters during pregnancy 2.
Do NOT use metformin for polycystic ovary syndrome beyond the first trimester 2.
Never mix insulin with other insulin products 6.
Never use insulin in an insulin pump for GDM management unless specifically indicated and monitored 6.
Do NOT inject insulin into a vein or muscle—only inject subcutaneously into the stomach area, upper arms, or thighs, rotating injection sites with each dose 6.
Postpartum Management
Women with GDM should be tested for persistent diabetes or prediabetes 4-12 weeks postpartum with a 75g oral glucose tolerance test using non-gestational criteria 3.
Women with a history of GDM are at increased risk of developing type 2 diabetes over time 3, 7.
Both metformin and intensive lifestyle intervention can prevent or delay progression to type 2 diabetes in women with a history of GDM 3.
Breastfeeding is recommended as it may reduce obesity in children and decrease maternal diabetes risk 7.