At what gestational age should delivery be considered for a fetus with macrosomia (fetal macrosomia)?

Timing of Delivery for Fetal Macrosomia

Delivery timing for fetal macrosomia should be determined by the severity of macrosomia and the presence of complications, with delivery recommended at 37 weeks for severe cases (EFW <3rd percentile or abnormal Doppler studies), at 38-39 weeks for moderate cases (EFW between 3rd-10th percentile with normal Doppler), and consideration of cesarean delivery only when estimated fetal weight exceeds 5000g in non-diabetic women or 4500g in diabetic women. 1

Delivery Timing Based on Severity of Macrosomia

Severe Macrosomia (EFW <3rd percentile or abnormal umbilical artery Doppler)

• Deliver at 37 weeks of gestation 1
• Earlier delivery may be indicated with:
  • Absent end-diastolic velocity: Deliver at 33-34 weeks 1
  • Reversed end-diastolic velocity: Deliver at 30-32 weeks 1

Moderate Macrosomia (EFW between 3rd-10th percentile)

• With normal umbilical artery Doppler: Deliver at 38-39 weeks of gestation 1

Suspected Large Macrosomia

• For non-diabetic women: Consider cesarean delivery only when EFW >5000g 1, 2
• For diabetic women: Consider cesarean delivery when EFW >4500g 1, 2

Management Considerations

Induction of Labor

• Suspected fetal macrosomia alone is not an indication for induction of labor 1
• Current evidence does not support early induction of labor for suspected macrosomia 1, 2
• Induction may double the risk of cesarean delivery without reducing shoulder dystocia or newborn morbidity 1

Mode of Delivery

• Labor and vaginal delivery are not contraindicated for women with estimated fetal weights up to 5000g in non-diabetic women 1
• For pregnancies with FGR complicated by absent/reversed end-diastolic velocity, cesarean delivery should be considered based on the clinical scenario 1
• Trial of labor has shown success rates of 72-82% for vaginal delivery even with macrosomic fetuses 3

Monitoring and Surveillance

• Once fetal growth restriction is diagnosed, serial umbilical artery Doppler assessment should be performed 1
• Weekly umbilical artery Doppler evaluation is suggested for severe FGR 1
• Weekly cardiotocography testing after viability for FGR without absent/reversed end-diastolic velocity 1

Risks and Complications

Maternal Risks

• Increased risk of cesarean delivery (risk doubles when EFW >4500g) 1
• Higher rates of postpartum hemorrhage and vaginal lacerations 2
• Lacerations requiring repair are more common when vaginal delivery is complicated by shoulder dystocia 3

Fetal/Neonatal Risks

• Shoulder dystocia (risk increases to 9.2-24% when birth weight >4500g in non-diabetic women) 1
• Brachial plexus injury and clavicular fracture (18-21 fold increased risk with birth weight >4500g) 1
• Decreased Apgar scores and increased risk of childhood obesity 2

Common Pitfalls and Caveats

• The diagnosis of fetal macrosomia is imprecise - ultrasound biometry is no better than clinical palpation 1
• Shoulder dystocia can occur unpredictably even in infants of normal birth weight 1
• Elective cesarean delivery reduces but does not eliminate the risk of birth trauma 1
• Midpelvic operative vaginal delivery should be avoided with suspected macrosomia 1
• With an estimated fetal weight >4500g, a prolonged second stage of labor or arrest of descent is an indication for cesarean delivery 1

By following these evidence-based guidelines for timing of delivery in fetal macrosomia, clinicians can optimize maternal and neonatal outcomes while minimizing unnecessary interventions.