At what gestational age should a patient with poorly controlled gestational diabetes mellitus (GDM) be delivered?

Timing of Delivery for Poorly Controlled Gestational Diabetes Mellitus

Patients with poorly controlled gestational diabetes mellitus should be delivered at 38-39 weeks' gestation, with evidence of maternal or fetal compromise warranting earlier delivery. 1

Assessment of Glycemic Control and Complications

• Poorly controlled GDM is characterized by:

  • Persistent fasting glucose >105 mg/dl (5.8 mmol/l) despite treatment
  • Postprandial glucose levels consistently above targets (1-hour >155 mg/dl or 2-hour >130 mg/dl)
  • Evidence of fetal macrosomia on ultrasound
  • Presence of maternal hypertensive disorders

• Maternal surveillance should include:

  • Blood pressure and urine protein monitoring at each visit to detect preeclampsia 1
  • Fetal growth assessment via ultrasound
  • Increased fetal surveillance when fasting glucose levels exceed 105 mg/dl 1

Timing of Delivery Algorithm

1. For poorly controlled GDM requiring medication (insulin/glyburide):

   • Deliver at 38-39 weeks' gestation 1, 2
   • Earlier delivery (before 38 weeks) is only indicated with objective evidence of maternal or fetal compromise 1

2. For well-controlled GDM (diet-controlled):

   • Delivery at 39 0/7 to 40 6/7 weeks' gestation 2, 3
   • Note: This is not applicable to the question about poorly controlled GDM

3. Indications for earlier delivery (before 38 weeks):

   • Fetal compromise (abnormal fetal testing)
   • Severe maternal hyperglycemia unresponsive to treatment
   • Development of preeclampsia
   • Evidence of placental insufficiency

Rationale for Timing Recommendations

The Fifth International Workshop-Conference on GDM clearly states that there are no data supporting delivery of women with GDM before 38 weeks' gestation in the absence of objective evidence of maternal or fetal compromise 1. However, evidence indicates that delivery past 38 weeks can lead to an increase in the rate of large-for-gestational-age infants without reducing cesarean delivery rates 1.

For poorly controlled GDM specifically:

• Fasting hyperglycemia >105 mg/dl is associated with increased risk of intrauterine fetal death during the last 4-8 weeks of gestation 1
• Prolongation of pregnancy beyond 38 weeks increases risk of fetal macrosomia without reducing cesarean rates 1
• The most recent evidence suggests delivery during the 39th week (39 0/7 to 39 6/7) for medication-controlled GDM provides the best balance of maternal and fetal outcomes 2, 3

Fetal Surveillance Prior to Delivery

• Intensify fetal surveillance when pregnancy continues beyond 40 weeks 1
• For poorly controlled GDM, begin fetal surveillance at 32 weeks 2, 3
• Surveillance methods include:
  • Non-stress testing
  • Biophysical profile
  • Doppler studies
  • Maternal monitoring of fetal movements

Important Caveats

• Estimated fetal weight >4,500g should prompt consideration of scheduled cesarean delivery 2, 4
• Corticosteroids for fetal lung maturity (if needed) should not be withheld due to GDM diagnosis, but will require intensified glucose monitoring and likely insulin adjustment 1
• Blood glucose monitoring during labor is recommended for women treated with insulin or glyburide 1
• Maternal glucose control should be optimized prior to delivery to prevent neonatal hypoglycemia

The decision for timing of delivery must balance the risks of prematurity against the risks of continued pregnancy with poor glycemic control, with 38-39 weeks representing the optimal window for most cases of poorly controlled GDM.