Management of prenatally detected structural anomalies

Principles · CNS (ventriculomegaly, neural tube defects) · Urinary tract (hydronephrosis, PUV) · Abdominal wall (gastroschisis, omphalocele) · Thorax (CDH, CCAM) · GI abnormalities · Cardiac anomalies · Skeletal dysplasias · Forfar & Arneil’s Pediatrics Ch.11

📌 Core principles: Multidisciplinary approach (MFM, neonatology, pediatric surgery, genetics). Confirm diagnosis, assess for associated anomalies, plan delivery at tertiary center, and coordinate postnatal intervention. Fetal therapy (shunts, laser, EXIT) available for select conditions.

📖 Prenatal structural anomalies – key management principles

🧠 CNS anomalies
Ventriculomegaly: assess progression, rule out spina bifida, aqueductal stenosis. Neural tube defects: MSAFP, ultrasound spine, plan Cesarean for large myelomeningocele, postnatal closure. Offer fetal surgery (myelomeningocele) in selected centers.
💧 Urinary tract
Hydronephrosis (AP diameter ≥7 mm 2nd trimester, ≥10 mm 3rd). Posterior urethral valves: oligohydramnios, keyhole sign. Severe obstruction → vesicoamniotic shunt. Postnatal VCUG, pyeloplasty.
🌐 Abdominal wall defects
Gastroschisis (right, no membrane): bowel exposure → risk of atresia, complex gastroschisis. Deliver at tertiary center, silo or primary closure. Omphalocele (central, membrane): screen for karyotype anomalies (trisomy 18,13, Beckwith‑Wiedemann).
🫁 Thorax (CDH, CCAM)
Congenital diaphragmatic hernia: assess lung‑to‑head ratio (LHR), liver herniation. FETO (tracheal occlusion) for severe cases. CCAM (cystic adenomatoid malformation): risk of hydrops → resection or thoracoamniotic shunt.
❤️ Cardiac & skeletal
Cardiac anomalies: fetal echocardiography, karyotype (22q11, trisomy 21). Plan delivery at cardiac center. Skeletal dysplasias: short long bones, thoracic hypoplasia → pulmonary insufficiency. Family studies, FGFR3 (achondroplasia).

📌 Multidisciplinary team (MDT) essential: fetal medicine, neonatology, pediatric surgery, cardiology, genetics, social work. Coordinate delivery timing, mode, location (tertiary center with NICU/PICU).

🔍 Approach to prenatally detected anomalies by system

CNS (ventriculomegaly ≥10 mm) – Detailed neurosonography, rule out neural tube defect, aqueductal stenosis, hemorrhage, infection. Karyotype ± microarray. Serial US to monitor progression. Isolated mild (<12 mm) often benign. Deliver at facility with neonatal neurology/neurosurgery.

Urinary tract (hydronephrosis AP ≥10 mm after 28 weeks) – Assess ureter, bladder, amniotic fluid. Bilateral severe hydronephrosis + oligohydramnios → suspect posterior urethral valves (PUV). Offer vesicoamniotic shunt if severe. Postnatal VCUG, renal scan, prophylactic antibiotics.

Abdominal wall defect – Gastroschisis (right, free loops) → bowel matting risk, associated atresia. Serial US, plan term delivery at surgical center. Omphalocele → karyotype, rule out Beckwith‑Wiedemann (macroglossia, neonatal hypoglycemia). C‑section for large defects.

Thoracic (CDH, CCAM) – CDH: LHR <1.0 indicates poor prognosis; liver herniation worsens outcome. Refer for possible FETO. CCAM >5 cm with hydrops → thoracoamniotic shunting or resection after delivery. Follow for pulmonary hypoplasia.

Cardiac & skeletal – Fetal echo, genetic testing (22q11, aneuploidy). Skeletal dysplasia: measure thoracic circumference, femur length. Achondroplasia → FGFR3 mutation. Plan for respiratory support at birth.

📋 Stepwise prenatal management of structural anomalies

Confirm diagnosis and exclude associated anomalies – Detailed fetal anatomy survey, fetal echocardiography, neurosonography. Amniocentesis for karyotype + microarray (especially for omphalocele, ventriculomegaly, cardiac defects).

Counsel family (non‑directive) – Explain natural history, available prenatal/postnatal interventions, survival, quality of life. Provide written information and contact with family support groups (e.g., CDH, spina bifida associations).

Plan delivery (timing, mode, location) – Tertiary care hospital with appropriate subspecialties (neonatal surgery, cardiology, NICU). C‑section for large myelomeningocele, giant omphalocele, EXIT for airway obstruction. Avoid preterm delivery unless maternal/fetal indications.

Consider fetal therapy (select conditions) – Laser for TTTS, vesicoamniotic shunt (PUV), thoracoamniotic shunt (hydrops with pleural effusion), FETO for severe CDH, fetal myelomeningocele repair (selected centers).

Postnatal transition plan – EXIT procedure for neck masses (teratoma, lymphatic malformation). Immediate neonatal team at delivery: airway management, venous access, early surgical consultation (gastroschisis, CDH, neural tube defect).

⚡ Key reminder: Isolated mild ventriculomegaly (10–12 mm) has good prognosis. Bilateral renal agenesis is lethal. Congenital diaphragmatic hernia with LHR <1.0 and liver up has high mortality.

🧠 Reflex prompts – structural anomalies

🤰 28 weeks: ventriculomegaly (15 mm), no other anomalies. Next step?
Serial US, fetal MRI, rule out aqueductal stenosis, hemorrhage. Isolated progressive → delivery at neurosurgical center. Postnatal VP shunt.
🧬 20 weeks: omphalocele containing liver. Most common associated anomaly?
Chromosomal (trisomy 18, 13, or Beckwith‑Wiedemann syndrome). Offer amniocentesis, microarray. Also screen for hypoglycemia after birth.
🫁 Left CDH, LHR 0.9, liver herniation. Prognosis?
Poor (<30% survival). Consider FETO (tracheal occlusion) at specialized fetal center. Severe pulmonary hypoplasia likely.
💧 Bilateral hydronephrosis, oligohydramnios, dilated posterior urethra (‘keyhole’ sign). Diagnosis?
Posterior urethral valves (PUV). Fetal vesicoamniotic shunt may preserve lung development. Postnatal valve ablation.
🌊 Fetal ascites, pleural effusion, skin edema. Next step in anomaly workup?
Hydrops fetalis (immune & non‑immune). Ultrasound for structural anomaly (CCAM, CDH, cardiac). TORCH/parvovirus, alpha‑thalassemia screening.
🦴 Short long bones, small chest, bowing. Likely diagnosis?
Skeletal dysplasia (thanatophoric, achondroplasia, osteogenesis imperfecta). Genetic testing (FGFR3, COL1A1/2). Assess thoracic circumference for pulmonary hypoplasia.