What is the best management approach for a pregnant woman with gestational diabetes mellitus (GDM)?

Management of Gestational Diabetes Mellitus

Start immediately with medical nutrition therapy and self-monitoring of blood glucose upon diagnosis, and if glycemic targets are not achieved within 1-2 weeks, initiate insulin as first-line pharmacologic therapy. 1

Initial Management Steps

Refer to a registered dietitian within the first week of diagnosis to develop an individualized nutrition plan that provides minimum 175g carbohydrate daily, 71g protein daily, and 28g fiber daily, emphasizing monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats. 1

• Begin self-monitoring of blood glucose immediately: check fasting glucose daily upon waking and postprandial glucose after each main meal (breakfast, lunch, dinner). 1

• Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week. 1

• For overweight women, calculate daily caloric intake at approximately 30-32 kcal/kg of pre-pregnancy body weight, plus an additional 340 kcal/day in the second trimester, typically totaling 2,000-2,200 kcal/day. 1

Glycemic Targets

Target the following glucose levels consistently throughout pregnancy:

• Fasting glucose <95 mg/dL 1, 2
• 1-hour postprandial <140 mg/dL 1, 2
• 2-hour postprandial <120 mg/dL 1, 2

Choose either 1-hour OR 2-hour postprandial measurements consistently—postprandial monitoring is superior to preprandial monitoring alone and is associated with better glycemic control and lower risk of preeclampsia. 1

When to Initiate Pharmacologic Therapy

If glycemic targets are not achieved within 1-2 weeks of lifestyle modifications alone, initiate insulin therapy immediately as the first-line pharmacologic agent because it does not cross the placenta to a measurable extent. 1, 2

Critical Pitfall to Avoid

Do not prematurely escalate to medications—70-85% of women can achieve glycemic targets with lifestyle modifications alone. 2, 3 Verify adequate lifestyle modifications including consultation with a registered dietitian, minimum dietary requirements, and physical activity before declaring treatment failure. 2

Insulin Prescribing Principles

When insulin is required:

• Use a smaller proportion as basal insulin and greater proportion as prandial insulin. 2
• Perform frequent titration as insulin requirements change dramatically throughout pregnancy. 2
• Avoid metformin and glyburide as first-line therapy due to their inferior outcomes and safety profiles compared to insulin—both cross the placenta. 1, 3

Monitoring During Pregnancy

Maternal Monitoring

• Continue daily fasting and postprandial blood glucose monitoring throughout pregnancy. 1
• Measure blood pressure and urinary protein at each prenatal visit to detect preeclampsia, as the risk of hypertensive disorders is increased in women with GDM. 1
• HbA1c has limited utility in GDM management but if used, measure monthly with a target HbA1c <6% (42 mmol/mol) if achievable without significant hypoglycemia—do NOT replace blood glucose monitoring with HbA1c because macrosomia results primarily from postprandial hyperglycemia, which HbA1c may not adequately detect. 1

Fetal Surveillance

• Begin ultrasound monitoring of fetal abdominal circumference in the second and early third trimesters and repeat every 2-4 weeks. 1
• Consider lower targets for glycemic control or intensification of pharmacologic therapy when fetal abdominal circumference is excessive (≥75th percentile for gestational age). 1
• Teach mothers to monitor fetal movements during the last 8-10 weeks of pregnancy and report immediately any reduction. 1

Delivery Timing

• For women with diet-controlled GDM meeting glycemic targets: deliver at 39-40 weeks of gestation. 1
• For women requiring insulin or with poor glycemic control: deliver at 39 weeks of gestation. 1

Critical Dietary Caveat

Never reduce carbohydrates below 175g/day minimum, as intakes below this threshold may compromise fetal growth when total energy intake is inadequate. 1

Postpartum Follow-Up

• Test all women with GDM for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g oral glucose tolerance test (OGTT) with non-pregnancy diagnostic criteria—do NOT use HbA1c at this visit because the concentration may still be influenced by changes during pregnancy and/or peripartum blood loss. 1

• Women with a history of GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years, requiring lifelong screening for diabetes at least every 3 years using standard non-pregnant criteria (annual HbA1c, annual fasting plasma glucose, or triennial 75-g OGTT). 1

Alternative Care Delivery

Telehealth visits for GDM patients can improve outcomes compared with standard in-person care, reducing cesarean delivery, neonatal hypoglycemia, and other complications. 2