Large for gestational age (LGA) refers to a neonate whose birth weight exceeds the 90th percentile for the given gestational age. These infants are often classified as macrosomic when weight is >4,000–4,500 g at term, though exact cutoffs vary by population and guidelines.

Pathophysiology

• Normal growth: Fetal size reflects maternal, placental, and genetic factors.

• Excess growth (LGA):

  • Often due to maternal metabolic or endocrine disorders, particularly diabetes mellitus, leading to increased transplacental glucose delivery.

  • Fetal hyperinsulinemia stimulates adipose deposition and somatic overgrowth.

• Other contributors: Maternal obesity, multiparity, post-term gestation, male sex of infant, or genetic syndromes.

Risk Factors

• Maternal:

  • Diabetes (pre-gestational or gestational)

  • Obesity

  • Excessive weight gain in pregnancy

  • Advanced maternal age

  • Multiparity

• Fetal:

  • Male sex

  • Beckwith-Wiedemann syndrome

  • Post-term pregnancy

Clinical Features

Complications

• Perinatal:

  • Birth trauma (shoulder dystocia, nerve injury, bone fractures)

  • Prolonged/difficult delivery, increased cesarean rate

• Metabolic:

  • Hypoglycemia (due to hyperinsulinemia)

  • Hypocalcemia and hypomagnesemia

  • Polycythemia → hyperbilirubinemia

• Respiratory:

  • Risk of transient tachypnea and respiratory distress syndrome

• Long-term:

  • Higher risk of obesity, insulin resistance, and metabolic syndrome later in life

Differential Diagnosis

Special Populations

• Preterm LGA:

  • Rare; often linked to maternal diabetes.

  • Increased risk of respiratory distress.

• Post-term infants:

  • May be LGA due to prolonged growth time.

Diagnosis

• Prenatal:

  • Ultrasound biometry (estimated fetal weight >90th percentile).

• Postnatal:

  • Plot birth weight on standardized growth charts for gestational age.

Management

1. Delivery considerations:

   • Anticipate shoulder dystocia or birth trauma.

   • Cesarean may be indicated for estimated fetal weight >4,500 g in diabetic mothers or >5,000 g in non-diabetic mothers.

2. Postnatal care:

   • Monitor blood glucose, calcium, magnesium, hematocrit.

   • Observe for respiratory distress.

   • Screen for birth trauma (fractures, nerve injury).

3. Long-term follow-up:

   • Counsel parents about increased risk of obesity and diabetes.

   • Encourage healthy nutrition and regular pediatric check-ups.

Patient counseling

• LGA means the baby is larger than expected for gestational age, usually because of maternal or fetal factors.

• Parents should be aware of possible birth complications and metabolic issues.

• Most complications can be prevented or managed with careful monitoring after birth.

• Long-term healthy lifestyle habits can reduce risks of obesity and metabolic disease.

Conclusion

Large for gestational age (LGA) describes infants above the 90th percentile for gestational age, most often due to maternal diabetes or obesity. These neonates are at increased risk of birth trauma, hypoglycemia, hypocalcemia, polycythemia, and respiratory complications. Recognition of risk factors, careful perinatal management, and structured follow-up are essential to optimize outcomes.

References

1. Cloherty JP, Eichenwald EC, Hansen AR, Stark AR. Manual of Neonatal Care. 8th ed. Philadelphia, PA: Wolters Kluwer; 2017.

2. Martin RJ, Fanaroff AA, Walsh MC. Fanaroff and Martin’s Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020.

3. American College of Obstetricians and Gynecologists. Fetal Macrosomia. Practice Bulletin No. 216. Obstet Gynecol. 2020;135(1):e18–e35.

4. Battaglia FC, Lubchenco LO. A practical classification of newborn infants by weight and gestational age. J Pediatr. 1967;71(2):159–163.