What features should be looked for in a child with macrosomia (fetal macrosomia, large for gestational age)?

Assessment of the Macrosomic Newborn

When evaluating a child with macrosomia (birth weight ≥4,000g), immediately assess for birth trauma complications—specifically brachial plexus injury, clavicular fracture, and hypoglycemia—while simultaneously screening for underlying maternal diabetes and associated congenital anomalies.

Immediate Neonatal Complications to Assess

Birth Trauma (Priority Assessment)

Brachial plexus injury is the most critical complication requiring immediate evaluation, with risk increased 18-to-21-fold when birth weight exceeds 4,500g 1, 2. Look for:

• Classic "waiter's tip" position indicating upper trunk (C5-C6) injury 2
• Preserved grasp reflex with weak Moro reflex suggests upper brachial plexus involvement rather than lower plexus injury 2
• Asymmetric arm movement or flaccid paralysis of the affected limb 2

Clavicular fracture occurs with 10-fold increased frequency in macrosomic infants and often accompanies brachial plexus injury 1, 2. Examine for:

• Crepitus, swelling, or asymmetry over the clavicle 2
• Decreased movement of the affected arm 2
• Obtain plain radiographs of chest/shoulder immediately to exclude fracture 2

Metabolic Complications

Hypoglycemia is a critical early complication requiring routine screening 3:

• Screen blood glucose within the first hours of life, particularly if maternal diabetes is present 3
• Macrosomic infants have 4.7-fold increased risk of neonatal hypoglycemia 4
• This occurs in 4% of macrosomic infants overall but is more common with maternal diabetes 5

Respiratory Complications

• Birth asphyxia and respiratory distress occur more frequently in macrosomic infants 3
• Assess Apgar scores and monitor for signs of respiratory compromise 3

Maternal History Assessment

Diabetes Screening (Most Critical Risk Factor)

Gestational diabetes is the single most common risk factor for macrosomia 6, with the following considerations:

• Undiagnosed/untreated gestational diabetes carries up to 20% macrosomia risk 1, 7
• Pre-existing Type 1 diabetes significantly increases LGA risk 6
• Gestational diabetes of any severity increases macrosomia risk, not just poorly controlled cases 6
• If maternal diabetes was present, the infant has 11.9-fold increased odds of macrosomia 4

Other Maternal Risk Factors to Document

• Maternal pre-pregnancy weight ≥80 kg is significantly associated with macrosomia 3
• Maternal age 30-39 years increases risk 3
• Multiparity is an independent risk factor 1, 3
• Previous history of macrosomic birth increases odds 3.3-fold 4
• Gestational age ≥40 weeks is associated with progressive macrosomia 1, 7

Screening for Associated Congenital Anomalies

In infants of mothers with uncontrolled diabetes, perform thorough examination for congenital anomalies 2:

• Cardiac defects (increased risk with maternal diabetes) 2
• Neural tube defects 2
• Caudal regression syndrome 2
• Consider renal ultrasound if other anomalies are detected, as genitourinary abnormalities are more common 2

Delivery Complications to Document

Maternal Complications

• Shoulder dystocia risk ranges from 9.2-24% in non-diabetic pregnancies with birth weight >4,500g, and 19.9-50% in diabetic pregnancies 1, 7
• Postpartum hemorrhage occurs more frequently 3
• Second-degree perineal tears are more common 3
• Prolonged labor 3

Critical Management Steps

Immediate Actions

1. Obtain plain radiographs of chest/shoulder to exclude clavicular or humeral fracture 2
2. Screen blood glucose routinely in all macrosomic infants 3
3. Document specific pattern of weakness if brachial plexus injury suspected 2

Early Referrals

• Refer to pediatric neurology or orthopedics within 1-2 weeks if weakness persists beyond the first few days 2
• Initiate physical therapy early (within first 2 weeks) to maintain range of motion and prevent contractures 2

Maternal Follow-up

Postpartum diabetes screening is essential 2:

• Perform 75g oral glucose tolerance test at 4-12 weeks postpartum 2
• Counsel about 50-70% lifetime risk of developing type 2 diabetes 2
• Emphasize importance of preconception glycemic control (A1C <6.5%) to reduce macrosomia risk from 20% to 2% in subsequent pregnancies 2

Common Pitfalls to Avoid

• Do not delay radiographs—clavicular fracture must be excluded immediately given 10-fold increased risk 2
• Do not provide false reassurance—while 80-90% of brachial plexus injuries recover fully within 3-6 months, parents need realistic expectations about the 10-20% risk of permanent deficit 2
• Do not assume normal glucose if infant appears well—hypoglycemia screening is mandatory regardless of clinical appearance 3