⁃ Maternal Inclusion Criteria:

• Singleton pregnancy

• Gestational age at screening is 19 to 25 5/7 weeks and gestational age at surgery is 22 to 25 6/7 weeks

• Maternal age: 18 years and older

• Body mass index ≤45 kg/m2 (pre-pregnancy)

• No preterm birth risk factors (short cervix \<20 mm or a history of previous preterm delivery)

• No previous uterine incision in the active uterine segment

• Willing to undergo an open fetal repair if the fetoscopic approach is unsuccessful

⁃ Fetal Inclusion Criteria:

• Spina bifida defect between T1 to S1 vertebral levels

• Chiari II malformation

• No evidence of kyphosis (curved spine)

• No major life-threatening fetal anomaly unrelated to spina bifida

• Normal karyotype, or a normal chromosomal microarray analysis (CMA), or a CMA with variants of unknown significance \[fluorescence in situ hybridization (FISH) acceptable if ≥ 24 weeks\].