What is the recommended management for fetal macrosomia?

Management of Fetal Macrosomia

Suspected fetal macrosomia is not an indication for induction of labor, as induction does not improve maternal or fetal outcomes. 1

Definition and Diagnosis

Fetal macrosomia is typically defined as a birth weight exceeding 4,000g (8lb, 13oz), with severe macrosomia defined as birth weight >4,500g. The diagnosis of fetal macrosomia is imprecise, with clinical estimation (Leopold's maneuvers) being as accurate as ultrasound biometry for weight estimation 1.

Risk Assessment and Prevention

Risk Factors:

• Previous macrosomic infant
• Maternal obesity
• Excessive gestational weight gain
• Gestational diabetes mellitus (GDM)
• Prolonged pregnancy

Prevention Strategies:

• For women with GDM: Tight glycemic control through diet, exercise, and insulin if necessary
• For all women: Appropriate weight gain during pregnancy
• Regular physical activity during pregnancy has been shown to reduce macrosomia risk 2

Management Algorithm

For Non-Diabetic Women:

1. Estimated Fetal Weight (EFW) <5,000g:

   • Labor and vaginal delivery are not contraindicated 1
   • Allow trial of labor with close monitoring
   • Expectant management until spontaneous labor or other indications for delivery arise
   • Delivery timing: 38-39 weeks if other indications exist 1

2. EFW >5,000g:

   • Consider prophylactic cesarean delivery 1
   • Particularly recommended for primiparous women 3

For Diabetic Women:

1. EFW <4,500g:

   • Trial of labor is appropriate
   • Delivery at 38 weeks is recommended to prevent further fetal growth 1

2. EFW >4,500g:

   • Consider prophylactic cesarean delivery 1

Labor Management:

• Avoid midpelvic operative vaginal delivery with suspected macrosomia 1
• With EFW >4,500g, a prolonged second stage or arrest of descent is an indication for cesarean delivery 1
• Be prepared for potential shoulder dystocia, which occurs in approximately 22% of vaginal deliveries of infants >4,500g 3

Special Considerations

Intrapartum Management:

• If cesarean delivery is performed, ensure adequate incision size to avoid difficult abdominal delivery 1
• Have experienced staff available for potential shoulder dystocia management
• Be prepared for potential birth trauma (clavicular fracture, brachial plexus injury) 1

Maternal Risks:

• Increased cesarean delivery rates
• Higher rates of postpartum hemorrhage
• Increased risk of vaginal and perineal lacerations 2

Fetal/Neonatal Risks:

• Shoulder dystocia (most common complication)
• Birth trauma (brachial plexus injury, clavicular fracture)
• Decreased Apgar scores
• Increased risk of childhood obesity 2

Common Pitfalls to Avoid

1. Unnecessary induction: Induction of labor for suspected macrosomia does not improve outcomes and may increase cesarean delivery rates 1, 4

2. Overreliance on ultrasound: Both clinical and ultrasonographic estimates of fetal weight are prone to error 4

3. Routine elective cesarean delivery: For suspected macrosomia <5,000g, this results in many unnecessary surgical procedures 1, 4

4. Inadequate preparation: When managing labor with suspected macrosomia, failure to prepare for potential shoulder dystocia can lead to adverse outcomes

5. Prolonging pregnancy: Delivery past 38 weeks in women with GDM can increase the rate of large-for-gestational-age infants without reducing cesarean delivery rates 1