This study aims to compare the maternal, fetal, and neonatal outcomes associated with the use of metformin versus glyburide for managing gestational diabetes.

The objective is to assess the safety and effectiveness profiles of both medications as potential alternatives to initiating insulin therapy.

Primary Outcome: treatment failure is defined as the initiation of insulin due to failure of glycemic control (more than 10% of high values using 4-point glucose checks) or side effects.

Secondary Outcomes:

Maternal:

• Percentage of fasting and postprandial glucose levels within target levels after initiation of treatment
• Incidence of maternal hypoglycemia
• Reported maternal side effects
• Maternal weight gain
• Preterm delivery
• Development of pregnancy-induced hypertension
• Labor dystocia.
• Instrumental delivery and its indication (fetal compromise, delay in progress, or maternal exhaustion)
• Mode of delivery
• Incidence of third and fourth perineal tear

Fetal and neonatal:

• Fetal large for gestational age
• Intrauterine fetal death
• Newborn weight
• Gestational age at delivery
• Neonatal birth injuries
• Stillbirth and neonatal death
• Apgar score at 1 minute

Inclusion Criteria:

• Pregnant women over 18 years old.
• Gestational age between 24 - 28 weeks.
• New diagnosis of gestational diabetes mellitus using a 2-hour glucose tolerance test.
• Medical therapy is indicated to control blood glucose following the failure of diet and lifestyle changes to solely achieve glycemic control (A2GDM).

Exclusion Criteria:

Patients with pre-gestational diabetes.

• First trimester fasting blood glucose ≥105 mg/dl or HbA1c > 6.4%.
• Major fetal anomalies.
• Intrauterine growth restriction (IUGR) before 24 weeks.
• Abnormal renal or liver function.
• Contraindications to metformin or glyburide.
• Medical treatment declined by the patient.
• Direct indication to commence insulin (initial fasting blood glucose >= 7 mmol/l or 126 mg/dl or >= 6 mmol/l or 108 mg/dl with macrosomia or polyhydramnios).
• Significant medical co-morbidities requiring continuous medical treatment in pregnancy.
• Non-compliance to blood glucose self-monitoring (missing 50% or more of total readings)