Inclusion Criteria:

• Pregnant women - maternal age 18 years or older.
• Gestational age at the time of the procedure between 19 0/7 weeks and 25 6/7 weeks.
• Singleton pregnancy.
• Myelomeningocele (Spina Bifida, "MMC"), diagnosis with the upper boundary located between Thoracic 1 (T1) and Sacral 1 (S1).
• Evidence of hindbrain herniation (confirmed on MRI to have an Arnold-Chiari type II malformation).
• Absence of chromosomal abnormalities and associated anomalies.
• Normal karyotype and/or normal chromosomal microarray (CMA) by invasive testing (amniocentesis or CVS). If there is a balanced translocation with normal CMA with no other anomalies the candidate can be included.
• Family has considered and declined the option of termination of the pregnancy at less than 24 weeks.
• Family meets psychosocial criteria (sufficient social support, ability to understand requirements for this study).
• Pregnant subject capable of consenting for their own participation in this study.
• Willingness to undergo an open MMC repair, if necessary.
• Parental/guardian permission (informed consent) for follow up of child after birth.

Exclusion Criteria:

• Fetal anomaly unrelated to MMC.
• Multiple gestation.
• Declined invasive testing for karyotype (amniocentesis or CVS).
• Severe kyphosis (defined as curvature of the spina (vertebras) higher than 30° measured by ultrasonography or magnetic resonance imaging).
• Increased risk for preterm labor including short cervical length (< 2.0 cm), history of incompetent cervix with or without cerclage, and previous preterm birth.
• Placental abnormalities (previa, abruption, accreta) known at time of enrollment.
• A body-mass index ≥ 40 at first prenatal visit.
• Contraindications to surgery including previous hysterotomy (whether from a previous classical cesarean, uterine anomaly such as an arcuate or bicornuate uterus, major myomectomy resection, or previous fetal surgery) in active uterine segment.
• Technical limitations precluding fetoscopic surgery, such as uterine fibroids, fetal membrane separation, uterine anomalies incompatible with fetoscopy.
• Amniotic Fluid Index (AFI) < 6 cm if deemed to be due to fetal anomaly, poor placental perfusion or function, or membrane rupture. Low amniotic fluid volume that responds to maternal hydration is not an exclusion.
• Maternal-fetal Rh isoimmunization, Kell sensitization or neonatal alloimmune thrombocytopenia affecting the current pregnancy.
• Maternal HIV, Hepatitis-B, Hepatitis-C status positive because of the increased risk of transmission to the fetus during maternal-fetal surgery. If the patients HIV or Hepatitis status is unknown, the patient must be tested and found to have negative results before enrollment.
• Maternal medical condition that is a contraindication to surgery or anesthesia.
• Patient does not meet other psychosocial criteria, as determined by the psychosocial interviewer using a standardized assessment, to handle the implications of the trial.
• Maternal hypersensitivity to collagen.
• Patient does not have a support person (i.e., spouse, partner, mother) available to support the patient for the duration of the pregnancy.
• Inability to comply with the travel and follow-up requirements of the trial.
• Participation in another intervention study that influences maternal and fetal morbidity and mortality or participation in this trial in a previous pregnancy.