Fetal and Prenatal Surgical Conditions
What prenatal diagnosis changes
Fetal surgery sits at the junction of obstetrics, genetics and neonatal surgery. The candidate must know which anomalies are found prenatally, which benefit from in-utero intervention, and which simply need planned delivery at a centre with neonatal surgical capability.
The core entities are congenital diaphragmatic hernia (CDH), congenital pulmonary airway malformation (CPAM), sacrococcygeal teratoma, myelomeningocele, lower urinary tract obstruction and giant cervical masses needing an EXIT procedure. In CDH two variables dominate prognosis: liver position (liver up is worse) and lung size, expressed as observed-to-expected lung-to-head ratio (O/E LHR). Severe disease is roughly O/E LHR below 25% with liver herniation, and fetoscopic tracheal occlusion is reserved for trial settings. CPAM is risk-stratified by the CPAM volume ratio (CVR = lesion volume divided by head circumference); CVR above 1.6 predicts hydrops, a short maternal steroid course may be used, and hydropic lesions may need fetal resection or shunting.
Traps
Examiners love the gastroschisis versus omphalocele distinction: gastroschisis has no sac, lies to the right of a normal cord insertion and is usually isolated, while omphalocele has a sac and carries chromosomal and Beckwith-Wiedemann associations. A second trap is assuming prenatal diagnosis improves outcome in every condition; for CDH it mainly allows delivery planning. Remember maternal risks of intervention: preterm labour, PPROM, oligohydramnios and uterine dehiscence.
Worked example
A 24-week fetus has a left cystic lung mass, CVR 1.9, no hydrops and no mediastinal shift. Rule of thumb: CVR above 1.6 means weekly surveillance and consideration of steroids; intervention is triggered by hydrops or worsening physiology, not by the CVR value alone.