What should be checked in a newborn with a single umbilical artery (SUA)?

Evaluation of Newborns with Single Umbilical Artery

For a newborn with isolated single umbilical artery (SUA), notify the pediatrician at delivery for thorough physical examination to detect occult structural anomalies, but routine renal ultrasonography is not necessary in asymptomatic infants without additional risk factors. 1

Immediate Postnatal Assessment

Physical Examination Priority

• The pediatrician should perform a comprehensive physical examination at birth, as up to 7% of fetuses with prenatal diagnosis of isolated SUA have structural anomalies detected postnatally. 1
• Focus the examination on cardiovascular and renal systems, as these are the most commonly affected organ systems when SUA occurs with structural abnormalities. 2, 1
• Cardiovascular anomalies show the strongest association with SUA, with odds ratios ranging from 5.9 to 20.3 for various cardiac defects. 2

Renal Screening Controversy

Evidence Against Routine Renal Imaging

• Routine postnatal renal ultrasonography is not warranted for asymptomatic newborns with isolated SUA. 3
• The largest series found no excess of significant renal malformations in isolated SUA compared to controls (1.6% vs 0.4%, p=0.74). 3
• When renal anomalies are detected in isolated SUA cases (approximately 16%), most are minor or self-limiting, with 54.5% being clinically insignificant. 4
• Cost-benefit analysis shows 14 isolated SUA cases need investigation to detect one major renal malformation, and most significant anomalies would be apparent with routine pediatric follow-up. 4

Contradictory Evidence for Screening

• Some older studies recommend routine renal ultrasonography, reporting 7.1% significant persisting abnormalities and 4.5% vesicoureteric reflux. 5
• However, these studies predate the era of routine comprehensive prenatal ultrasound, which now identifies most significant structural anomalies antenatally. 3

Clinical Algorithm for Renal Evaluation

• Perform renal ultrasonography only if:
  • Additional structural anomalies are present on physical examination (8 of 8 infants with coexistent systemic malformations had abnormal renal imaging) 3
  • Clinical signs or symptoms suggestive of renal pathology develop 6
  • Additional risk factors for malformations exist 4

Growth Monitoring

Increased Risk of Growth Restriction

• Neonates with isolated SUA have significantly higher incidence of small for gestational age (35.7% vs 3.6%, p=0.011) and reduced body length. 7
• Placental weight is significantly lighter in SUA cases (597.1±175.4g vs 709.3±95.2g, p=0.010), likely contributing to growth restriction. 7
• Document birth weight, length, and head circumference carefully, with close pediatric follow-up for growth parameters. 7

Genetic Considerations

No Additional Chromosomal Testing Needed

• If aneuploidy screening was negative or not performed prenatally, no additional genetic testing is needed postnatally for isolated SUA. 1
• Isolated SUA shows no increased risk of aneuploidy according to current guidelines. 2, 1
• When SUA occurs with other structural abnormalities, aneuploidy frequency ranges from 4-50%, but this does not apply to truly isolated cases. 2

Common Pitfalls to Avoid

• Do not reflexively order renal ultrasound on all SUA infants—this represents low-value care in the modern era of comprehensive prenatal imaging. 3
• Do not miss the 7% of infants with occult structural anomalies—ensure thorough physical examination by an experienced pediatrician. 1
• Do not overlook growth monitoring—SUA infants have significantly increased risk of being small for gestational age requiring closer follow-up. 7
• Do not forget to review prenatal records—if third-trimester growth ultrasounds and antenatal surveillance were performed as recommended, this provides additional reassurance. 8, 1