Situs Inversus in Fetus: Diagnosis, Associations, and Pregnancy Management
Situs Inversus: Fetal Findings and Implications
Situs inversus totalis: complete mirror-image reversal of thoracic and abdominal viscera (incidence ~1:10,000). Stomach on right, liver on left, heart apex right (dextrocardia).
Etiology
- Ciliary dyskinesia in embryonic node (nodal flow determines left-right axis).
- Genetic: autosomal recessive (DNAH5, DNAI1, others); 25% recurrence if both parents carriers.
- Associated with primary ciliary dyskinesia (PCD/Kartagener syndrome): chronic sinusitis, bronchiectasis, infertility.
Prenatal Diagnosis
- Ultrasound: 4-chamber heart view (apex right), stomach bubble right, liver left.
- Typically detected 18-22 week anatomy scan.
- Fetal echo essential: 3-5% have congenital heart disease (CHD) – ASD, VSD, AV canal, TGA.
Associated Anomalies
- CHD (most significant), intestinal malrotation, biliary atresia, renal anomalies.
- If isolated situs inversus + normal heart → excellent prognosis.
Pregnancy & Delivery Management
- Serial growth scans (IUGR risk with CHD).
- Delivery at tertiary center if CHD or malrotation suspected.
- Neonatal evaluation: cardiac echo, abdominal US, ciliary function testing if PCD suspected.
Long-Term Outlook
Isolated situs inversus: normal lifespan, no restrictions. Medical alert bracelet recommended (dextrocardia alters ECG, exam findings). PCD requires multidisciplinary respiratory care.
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