Gestational Diabetes Mellitus (GDM)

Pregnancy

36 y/o G2P1001 with h/o previous GDM/macrosomia in pregnancy, physical inactivity, non-European heritage, and a first degree relative with diabetes mellitus type 2 presents for prenatal care. Weight gain > 11 lbs since age 18 years and BMI > 25 kg/m^2.

• Initial visit

  • Positive urine beta-hCG test in office

  • BMI > 25 kg/m^2 + 1 risk factor (see notes below): Obtain HbA1c

• GDM screening at 24-28 WGA with 50 g 1 hour glucose tolerance test

  • Patient instructed to fast for 8 hours prior to test

  • Goals (mg/dL): Fasting < 95, 1 hour < 140

  • Failed 1 hour test (any value greater than goal): Schedule 100 g 3 hour test

• HbA1c > 6.4% or positive 3 hour glucose test: Patient advised to monitor fasting (goal < 95 mg/dL) and 1 hour postprandial (goal < 140 mg/dL) levels.

  • Nutrition and weight management

    • Advised to maintain total pregnancy weight gain < 40 lbs

    • Recommend 30 minutes moderate aerobic exercise daily

    • Refer for nutrition consult

  • Start metformin 500 mg daily if > 50% home values exceed goals and titrate to 1,000 mg BID per fingersticks. For additional control, continue metformin and

    • Start insulin glargine 0.3 u/kg daily and increase dose by 10% weekly until ≥ 5 daily fasting fingersticks are < 95 mg/dL or patient experiences hypoglycemia (fingerstick < 70 mg/dL)

    • Elevated postprandial fingersticks despite maximum glargine: Start insulin aspart 0.1 u/kg TID premeal

• Antenatal Testing and Delivery

  • Consult Maternal Fetal Medicine at time of diagnosis

  • Obtain growth ultrasound at 37 WGA and offer schedule c-section for estimated fetal weight > 4,500 g

  • Induction

    • GDMA1: Offer at 39+0 WGA and perform at 41+0 WGA if still pregnant

    • GDMA2: Schedule induction of labor at 39 WGA due to increased risk for stillbirth

• Postpartum

  • Obtain fasting glucose at 6 and 12 week follow-up appointments

  • Screen for DM using HbA1c every 3 years following delivery

Intrapartum Management

GDMA1

• Obtain fingersticks q4 hours

• Fluids: Fingerstick (mg/dL)

  • ≥ 70: Normal saline at 125 cc/hr

  • < 70: D5NS at 125 cc/hr

Well controlled GDMA2

• Obtain fingersticks q2 hours in latent labor and q1 hour in active labor

• Fluids: Fingerstick (mg/dL)

  • ≥ 100: Normal saline at 125 cc/hr

  • < 100: D5NS at 125 cc/hr

• Glucose control

  • Initial: Continue oral and basal insulin, hold mealtime insulin

  • Two fingersticks > 150 mg/dL: Convert to poorly controlled protocol (see below)

Poorly controlled GDMA2

• Obtain fingersticks q1 hours

• Start D5NS at 125 mL/hr

• Start insulin drip

  • Initial fingerstick: < 80 mg/dL (0 u/hr), 80-120 (0.5), 121-140 (1), 141-180 (1.5), 181-220 (2), > 220 (2.5)

  • Adjust per protocol

Notes

• Risk factors for GDM

  • Age > 35 years

  • Past medical history: GDM, macrosomia in pregnancy

  • Family history: Non-European heritage, first degree relative with hypertension and/or diabetes mellitus

  • Physical exam: Weight gain > 11 lbs since age 18 years, BMI > 25 kg/m^2

• Three hour glucose tolerance test

  • Positive if two values values > goals

  • Goals (mg/dL): Fasting < 95, 1 hour < 180, 2 hour < 155, 3 hour < 140

• GDMA1 vs. GDMA2

  • GDMA1: Glucose controlled with lifestyle alone

  • GDMA2: Medication required to control glucose

• Management

  • There is no strong evidence showing that dietary counseling improves outcomes

  • Medications

    • Oral medications safe in pregnancy include metformin and glyburide

    • Pharmacologic management decreases risk for maternal preeclampsia, large for gestational age infants, operative delivery, and shoulder dystocia