What are the guidelines for managing gestational diabetes mellitus (GDM) in a pregnant woman in the Philippines?

Gestational Diabetes Mellitus Guidelines in the Philippines

Begin management immediately with medical nutrition therapy, self-monitoring of blood glucose, and physical activity, 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 with lifestyle modifications alone, initiate insulin therapy as the first-line pharmacologic agent. 1, 2, 3

Initial Management: Lifestyle Modifications

Medical Nutrition Therapy:

• Refer to a registered dietitian nutritionist familiar with GDM management within the first week of diagnosis to develop an individualized nutrition plan 2, 3
• The diet must provide minimum daily requirements of 175g carbohydrates, 71g protein, and 28g fiber 1, 2
• Distribute carbohydrates across three small-to-moderate meals and 2-4 snacks throughout the day to limit postprandial glucose excursions 3
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 1, 2
• Critical pitfall to avoid: Do not reduce carbohydrates below 175g/day, as this may compromise fetal growth when total energy intake is inadequate 2

Physical Activity:

• Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week 2, 3
• Exercise interventions improve glucose outcomes and reduce the need to start insulin or decrease insulin dose requirements 1

Blood Glucose Monitoring

Self-Monitoring Protocol:

• Check fasting glucose daily upon waking 2
• Check postprandial glucose after each main meal (breakfast, lunch, dinner) 2
• Glycemic targets: Fasting <95 mg/dL, 1-hour postprandial <140 mg/dL, or 2-hour postprandial <120 mg/dL 1, 2, 3
• A1C should be used as a secondary measure only, not as the primary monitoring tool, as it represents an average and may not capture physiologically relevant glycemic parameters in pregnancy 1, 3

When to Initiate Pharmacologic Therapy

Insulin as First-Line Agent:

• Add insulin if glycemic targets are not achieved within 1-2 weeks of lifestyle modifications alone 2, 3
• Insulin is the preferred and recommended first-line pharmacologic agent because it does not cross the placenta to a measurable extent 1, 2, 4, 3
• Initial total daily insulin dose should be calculated as 0.7-1.0 units/kg of current weight, distributed as 40% basal insulin and 60% prandial insulin 3
• All insulins are pregnancy category B except for glargine and glulisine, which are labeled C 1

Avoid Oral Agents as First-Line:

• Metformin and glyburide should not be used as first-line agents, as both lack long-term safety data 1, 2
• The Endocrine Society specifically recommends avoiding metformin and glyburide as first-line therapy due to their inferior outcomes and safety profiles compared to insulin 2
• Up to 46% of women started on metformin may require additional insulin to maintain expected blood glucose levels 5

Expected Outcomes with Lifestyle Modifications

• 70-85% of women diagnosed with GDM under Carpenter-Coustan criteria can control GDM with lifestyle modification alone 1
• This proportion is anticipated to be even higher if the lower International Association of the Diabetes and Pregnancy Study Groups diagnostic thresholds are used 1
• Treatment has been demonstrated to improve perinatal outcomes in randomized studies 1

Specialized Care and Monitoring

Team-Based Approach:

• Referral to a specialized center is recommended if this resource is available, due to the complexity of insulin management in pregnancy 1
• Team-based care through interprofessional team members improves outcomes 3
• Telemedicine interventions used in combination with in-person visits demonstrate reduced incidences of cesarean delivery, premature rupture of membranes, pregnancy-induced hypertension or preeclampsia, preterm birth, neonatal asphyxia, and polyhydramnios compared with standard in-person care alone 1, 3

Fetal Monitoring:

• Regular obstetric examinations including ultrasound examinations are recommended to minimize maternal and fetal/neonatal morbidity and perinatal mortality 6

Postpartum Management

Immediate Postpartum:

• Test for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g oral glucose tolerance test with non-pregnancy diagnostic criteria 1, 2, 4
• Women with a history of GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years 2

Long-Term Follow-Up:

• If glucose tolerance is normal postpartum, reassess glucose parameters every 1-3 years depending on other risk factors 1
• Both metformin and intensive lifestyle intervention prevent or delay progression to diabetes in women with a history of GDM; only 5-6 individuals need to be treated with either intervention to prevent one case of diabetes over 3 years 1

Breastfeeding and Contraception:

• All women should be supported in attempts to breastfeed their babies, given immediate nutritional and immunological benefits, with potential longer-term metabolic benefit to both mother and offspring 1
• A contraceptive plan should be discussed and implemented with all women with diabetes of reproductive potential 4
• Effective contraception must be used until glycemic targets are achieved in future pregnancies 4

Common Pitfalls to Avoid

• Do not delay insulin initiation in women with poor glycemic control on lifestyle modifications 3
• Do not rely solely on A1C for monitoring, as it may not capture physiologically relevant glycemic parameters in pregnancy 3
• Do not use metformin for polycystic ovary syndrome beyond the first trimester 3
• Do not reduce carbohydrates below 175g/day, as this may compromise fetal growth 2