We conducted the trial at three maternal–fetal surgery centers — the Children's Hospital of Philadelphia, Vanderbilt University, and the University of California, San Francisco — together with an independent data-coordinating center at George Washington University and with the Eunice Kennedy Shriver National Institute of Child Health and Human Development. All other fetalintervention centers in the United States agreed not to perform prenatal surgery for myelomeningocele while the trial was ongoing. The trial was approved by the institutional review board at each center. The study protocol, including the statistical analysis plan and full inclusion and exclusion criteria, is available with the full text of this article at NEJM.org.
Inclusion criteria were a singleton pregnancy, myelomeningocele with the upper boundary located between T1 and S1, evidence of hindbrain herniation, a gestational age of 19.0 to 25.9 weeks at randomization, a normal karyotype, U.S. residency, and maternal age of at least 18 years. Major exclusion criteria were a fetal anomaly unrelated to myelomeningocele, severe kyphosis, risk of preterm birth (including short cervix and previous preterm birth), placental abruption, a body-mass index (the weight in kilograms divided by the square of the height in meters) of 35 or more, and contraindication to surgery, including previous hysterotomy in the active uterine segment.