Fetal Surgery

1. INTRODUCTION

• Definition: Operative interventions performed on the fetus in-utero to correct severe congenital anomalies.
• Paradigm: Transforms the fetus from a passive passenger to a patient requiring direct care.
• Goal: To convert a fatal or severely debilitating condition into a survivable or manageable one.
• The "Two-Patient" Concept: Unique surgical challenge involving two patients—the mother (bystander accepting risk) and the fetus (beneficiary).

2. SELECTION CRITERIA (IFMSS / Eurofetus Guidelines)

Intervention is justified only if:

1. Diagnosis: Accurately established (Level II USG, MRI, Karyotype/Microarray).
2. Natural History: The condition is lethal or causes severe morbidity if left untreated.
3. Absence of Other Defects: No co-existing lethal genetic/structural anomalies.
4. Feasibility: The procedure is technically possible and proven in animal/human trials.
5. Safety: Maternal risk is minimal and clearly defined.
6. Consent: Comprehensive counseling regarding risks to current and future pregnancies.

3. CLASSIFICATION OF SURGICAL MODALITIES

Fetal surgery is classified by the level of invasiveness and access route.

A. Percutaneous Ultrasound-Guided Procedures (Needle-based)

Least invasive; performed under local anesthesia + sedation.

1. Shunt Placement (Catheters):
   • Thoraco-Amniotic Shunt: For massive Pleural Effusion/Chylothorax (Hydrops).
   • Vesico-Amniotic Shunt: For Lower Urinary Tract Obstruction (LUTO/PUV).
     • Goal: Relieve bladder obstruction to preserve renal function and amniotic fluid (prevent pulmonary hypoplasia).
2. Radiofrequency Ablation (RFA):
   • Indication: TRAP sequence (Twin Reversed Arterial Perfusion) in monochorionic twins.
   • Action: Coagulation of the acardiac twin's cord to protect the pump twin from cardiac failure.
3. Intrauterine Transfusion (IUT):
   • Accessing the umbilical vein for anemia correction.

B. Fetoscopic Surgery (Minimally Invasive)

Uses small endoscopes (2–3 mm) via trocars; reduced maternal morbidity compared to open surgery.

1. Fetoscopic Laser Photocoagulation:
   • Gold Standard for Twin-Twin Transfusion Syndrome (TTTS).
   • Technique: Selective ablation of communicating placental vessels (Solomon technique).
2. FETO (Fetoscopic Endoluminal Tracheal Occlusion):
   • Indication: Severe Congenital Diaphragmatic Hernia (CDH).
   • Principle: A balloon occludes the trachea (26–28 weeks) $\to$ Lung fluid is trapped $\to$ Lungs expand against the herniated viscera ("Stretch to Grow").
   • Removal: Balloon removed at 34 weeks or during EXIT.
3. Amniotic Band Lysis:
   • Laser or sharp division of bands threatening limb amputation.

C. Open Fetal Surgery

Requires maternal laparotomy and hysterotomy. Highest risk profile (uterine rupture, preterm labor).

1. Myelomeningocele (MMC) Repair:
   • Study: MOMS Trial (Management of Myelomeningocele Study).
   • Technique: Exposure of fetal back $\to$ Layered closure of dura, muscle, and skin.
   • Benefit: Reduced Chiari II malformation reversal, reduced hydrocephalus (shunt need), improved ambulation.
2. CCAM/CPAM Resection:
   • Lobectomy for massive lung lesions causing mediastinal shift and hydrops.
3. Sacrococcygeal Teratoma (SCT) Resection:
   • For highly vascular tumors causing high-output cardiac failure.

D. EXIT Procedure (Ex Utero Intrapartum Treatment)

• Concept: Controlled delivery preserving placental circulation.
• Indication: CHAOS (Congenital High Airway Obstruction Syndrome), Giant Cervical Teratoma.
• Steps:
  1. Deep general anesthesia (uterine relaxation).
  2. Fetal head/shoulders delivered; cord remains warm and pulsing inside uterus.
  3. Airway secured (Laryngoscopy $\to$ Bronchoscopy $\to$ Tracheostomy).
  4. Cord clamped only after ventilation is established.

4. PERIOPERATIVE MANAGEMENT

The success of fetal surgery relies heavily on preventing the primary complication: Preterm Labor.

1. Tocolysis: Indomethacin (pre-op) and Magnesium Sulfate (intra-op) to prevent uterine contractions.
2. Maternal Anesthesia: General anesthesia (Open/EXIT) or Regional/Local (Fetoscopy).
3. Antenatal Steroids:
   • Given the high risk of preterm delivery post-procedure, administration of Betamethasone or Dexamethasone is standard.
   • Regimen: Betamethasone 12 mg IM x 2 doses.
   • Goal: Accelerate fetal lung maturation to reduce RDS and IVH if the surgery precipitates delivery.

5. SPECIFIC INDICATIONS AND EVIDENCE

A. Myelomeningocele (Spina Bifida)

• Pathophysiology: "Two-Hit Hypothesis".
  • Hit 1: Failure of neural tube closure.
  • Hit 2: Chemical injury to exposed cord by amniotic fluid.
• Surgery: Intrauterine closure stops "Hit 2".
• MOMS Trial Results:
  • Shunt placement: Reduced from 82% (postnatal) to 40% (prenatal).
  • Mental development: Improved scores.
  • Motor function: doubled independent walking ability.
• Risks: Preterm birth (avg 34 weeks), placental abruption.

B. Twin-Twin Transfusion Syndrome (TTTS)

• Stage: Quintero Stages II–IV.
• Procedure: Laser coagulation of AV anastomoses.
• Outcome: Survival of at least one twin >75%; reduced neurologic morbidity compared to serial amnioreduction.

C. Congenital Diaphragmatic Hernia (CDH)

• Predictor: Lung-Head Ratio (LHR) <1.0 (observed/expected <25%) indicates severe hypoplasia.
• TOTAL Trial: Showed significant survival benefit of FETO in severe left-sided CDH.

6. COMPLICATIONS

Maternal (The "Innocent Bystander")

• Surgical: Hemorrhage, Infection, Bladder injury.
• Obstetric:
  • Preterm Labor / PPROM: The most common complication.
  • Uterine Rupture: Risk in future pregnancies (requires C-section for all future deliveries after open surgery).
  • Pulmonary Edema: Due to tocolytics (magnesium/beta-mimetics).

Fetal

• Death: Procedure-related mortality.
• Bradycardia: During cord manipulation.
• Prematurity: Sequelae of early birth (RDS, NEC).

7. ETHICAL CONSIDERATIONS

• Maternal-Fetal Conflict: Balancing maternal autonomy and risk against fetal benefit.
• Innovations: Moving from "Experimental" to "Standard of Care".
• Cost: High resource utilization (NICU, lifelong follow-up).

8. FUTURE HORIZONS

• Tissue Engineering: Use of amniotic fluid stem cells to repair defects (e.g., diaphragmatic patches).
• Gene Editing (CRISPR): In-utero correction of monogenic diseases (SMA, CF) before irreversible damage occurs.
• Microneurosurgery: Fetoscopic repair of Myelomeningocele (reducing maternal hysterotomy risks).