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:

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

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

Least invasive; performed under local anesthesia + sedation.

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).
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.
Intrauterine Transfusion (IUT):
- Accessing the umbilical vein for anemia correction.

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

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

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

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

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 $\rightarrow$ Bronchoscopy $\rightarrow$ Tracheostomy).
4. Cord clamped only after ventilation is established.

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

Tocolysis: Indomethacin (pre-op) and Magnesium Sulfate (intra-op) to prevent uterine contractions.
Maternal Anesthesia: General anesthesia (Open/EXIT) or Regional/Local (Fetoscopy).
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.

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.

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.

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.

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).

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).

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).