Since 1997, 180 fetuses have had in utero closure of myelomeningocele (MMC) by open fetal surgery. Preliminary clinical evidence suggests that this procedure reduces the incidence of shunt-dependent hydrocephalus and restores the cerebellum and brainstem to more normal configuration. However, clinical results of fetal surgery for MMC are based on comparisons with historical controls and examine only efficacy and not safety. The Myelomeningocele Repair Randomized Trial is a multi-center unblinded randomized clinical trial of 200 patients that will be conducted at three Fetal Surgery Units (FSU), the University of California-San Francisco, Children's Hospital of Philadelphia, and Vanderbilt University Medical Center, along with an independent Data and Study Coordinating Center, the George Washington University Biostatistics Center. The primary objective of the trial is to determine if intrauterine repair of fetal myelomeningocele at 18¿ to 256 weeks gestation improves outcome, as measured by 1) death or the need for ventricular decompressive shunting by one year of life and 2) death or Bayley Mental Development Index, as compared '.o standard postnatal repair Consenting patients who satisfy eligibility criteria will be centrally randomized to either intrauterine or standard postnatal repair of the MMC. Patients assigned to the fetal surgery group will be discharged to nearby accommodation following surgery, unless infeasible, in which case they will return to their assigned FSU at 32¿ weeks gestation for delivery at 37¿ weeks gestation by cesarean section. Patients assigned to the postnatal surgery group will return home and at 37¿ weeks, return to their assigned FSU for delivery by cesarean section. Magnetic Resonance Imaging will be conducted at enrollment, discharge or term gestation, and one year of age to determine if intrauterine repair improves the degree of the Chiari II malformation. Neonatal morbidity will be recorded as will the number of surgical procedures for conditions related to the MMC, muscle strength, ambulation status and urinary and fecal continence. Infants will make followup visits at twelve and thirty months corrected age for detailed neuromotor function analysis, cognitive testing and evaluation of neurodevelopmental status. In addition, the long term psychosocial and reproductive consequences in mothers will be evaluated. In summary, the proposed trial will be able to demonstrate whether fetal intervention offers improved outcome with a reasonable quality of life for spina bifida children.