Is q22 deletion syndrome visible on a standard fetal ultrasound?

Can 22q11.2 Deletion Syndrome Be Detected on Fetal Ultrasound?

22q11.2 deletion syndrome can show up on fetal ultrasound, but detection is inconsistent and depends on the presence of structural anomalies—cardiac defects are most reliably visualized, while many affected fetuses have normal ultrasounds. 1

Timing and Detection Rates

Prenatal features may be observed on fetal ultrasound/echocardiogram in the first trimester, but more commonly at ≥20 weeks' gestation. 1 The detection is highly variable because:

• Not all congenital features are appreciated prenatally (e.g., laryngeal web, thymic hypoplasia may be missed) 1
• Extracardiac abnormalities affecting all systems can be present in as many as 90% of cases, but their visibility on ultrasound varies 1
• The fetal phenotype is poorly described and inconsistent across cases 2

Most Detectable Features on Ultrasound

Cardiac Anomalies (Most Reliable Indicator)

Conotruncal heart defects are the most common and reliably detected anomalies, occurring in approximately 65-68% of affected fetuses. 3, 2 These include:

• Tetralogy of Fallot 1, 2
• Interrupted aortic arch type B 1
• Truncus arteriosus 1
• Ventricular septal defects 1
• Other vascular anomalies including aberrant subclavian artery and aortic arch anomalies 1

All fetuses with conotruncal anomalies detected prenatally had 22q11.2 deletion confirmed in one prenatal series. 4

Other Detectable Structural Abnormalities

Additional features that may be visualized include:

• Urinary tract malformations (present in 25 fetuses in one pathology series) 2
• Intrauterine growth restriction 1, 5
• Polyhydramnios (potential for preterm labor) 1, 5
• Cavum septi pellucidi dilatation 5
• Skeletal anomalies (less specific association) 5

Rarely Detected Severe Features

Severe neurological abnormalities including neural tube defects and arhinencephaly have been identified in fetal cases, though these are unusual. 2 Lethal malformations such as hypoplastic left heart syndrome, bilateral renal agenesis, and tracheal agenesis have also been reported. 2

Critical Limitations of Ultrasound Screening

The absence of ultrasound findings does NOT rule out 22q11.2 deletion syndrome. Several important caveats:

• Thymic defects occur in approximately 62-63% of cases but are difficult to visualize reliably on standard ultrasound 3, 2
• Many affected fetuses have subtle or no detectable structural anomalies 5, 4
• Detection depends heavily on gestational age, ultrasound quality, and operator expertise 5
• Most prenatal sonographic findings are rather common and non-specific, making systematic 22q11.2 testing based on isolated findings not justifiable 4

Clinical Action When Ultrasound Abnormalities Are Found

When ultrasound anomalies are detected, immediate referral to maternal-fetal medicine and genetic counseling is warranted. 1 The recommended pathway is:

1. Prenatal diagnostic testing via chorionic villus sampling or amniocentesis is recommended to optimize delivery planning 1
2. Chromosomal microarray (CMA) remains the most comprehensive diagnostic test 1, 5
3. Noninvasive prenatal screening (NIPS) can detect 22q11.2 deletions with 70-83% detection rate and 40-50% positive predictive value, but requires confirmatory diagnostic testing 5, 6

Management Implications of Prenatal Detection

Fetuses with confirmed 22q11.2 deletion should be considered high risk for pregnancy/delivery given elevated prevalence of late preterm births and intrauterine growth restriction. 1 This requires:

• Close monitoring for congenital heart disease (cardiac function surveillance) 1
• Monitoring for polyhydramnios 1
• Location and mode of delivery may be influenced by the diagnosis with or without structural anomalies 1

In summary: while cardiac defects and some structural anomalies can be detected on ultrasound, many affected fetuses will have normal imaging, making genetic testing essential when 22q11.2DS is suspected based on family history or suggestive findings. 5