Fetal Aortic Valvuloplasty for Evolving Hypoplastic Left Heart Syndrome

Inclusion Criteria * Pregnant women 18-45 years of age. * Gestational age between 21 0/7 and 29 6/7 weeks of gestation * The mother must be healthy enough to undergo surgery. * The individual being enrolled must be able to provide informed consent. * Dominant cardiac defect is valvar * Evolving hypoplastic left heart syndrome defined as depressed left ventricle systolic and at least one of the following: * Retrograde flow in the transverse aortic arch * Two of the following: (1) left to right flow across the atrial septum (bulging of the septum left to right in cases of intact atrial septum); (2) monophasic mitral valve inflow; (3) bidirectional flow in the pulmonary veins. * Potential for a technically successful and postnatal biventricular outcome defined as left ventricle long axis Z-score equal or greater than -2 PLUS at least 4 of the following 5 criteria: * Left ventricle long axis Z-score more than zero * Left ventricle short axis Z-score more than zero * Aortic annulus Z-score more than -3.5 * Mitral valve annulus Z-score more than -2 * Left ventricle generating a maximal instantaneous gradient (MIG) equal or greater than 20 mmHg (or by mitral regurgitation jet greater than or equal to 20 mmHg). Exclusion Criteria * Patient is less than 18 years of age or more than 45 years of age. * Contraindication to anesthesia or surgery * Preterm labor or cervical length \<20 mm at enrollment or uterine anomaly strongly predisposing to preterm delivery. * Other fetal anomalies that significantly impact fetal/neonatal survival (e.g., congenital diaphragmatic hernia, bilateral renal agenesis, etc.) * Fetal aneuploidy and pathogenic findings on Karyotype or Microarray that impact significantly the fetal/neonatal survival. * Cases with all the following criteria: * Left ventricle pressure ≤ 47 mmHg * MV dimension Z-score \< 0.1 * MV inflow time Z-score \< -2