four cases were performed before stopping the procedure - two of the four fetuses died. 1998 – n. scott adzick and team at the children's hospital of philadelphia performed open fetal surgery for spina bifida in an early gestation fetus (22-week gestation fetus) with a successful outcome. open fetal surgery for myelomeningocele involves surgically opening the pregnant mother's abdomen and uterus to operate on the fetus. the exposed fetal spinal cord is covered in layers with surrounding fetal tissue at mid-gestation (19–25 weeks) to protect it from further damage caused by prolonged exposure to amniotic fluid. between 1998 and 2003, dr. adzick, and his colleagues in the center for fetal diagnosis and treatment at the children's hospital of philadelphia, performed prenatal spina bifida repair in 58 mothers and observed significant benefit in the babies. fetal surgery after 25 weeks has not shown benefit in subsequent studies. moms trial management of myelomeningocele study (moms) was a phase iii clinical trial designed to compare two approaches to the treatment of spina bifida: surgery before birth and surgery after birth. the trial concluded that the outcomes after prenatal spina bifida treatment are improved to the degree that the benefits of the surgery outweigh the maternal risks. this conclusion requires a value judgment on the relative value of fetal and maternal outcomes on which opinion is still divided. to be specific, the study found that prenatal repair resulted in: reversal of the hindbrain herniation component of the chiari ii malformation reduced need for ventricular shunting (a procedure in which a thin tube is introduced into the brain's ventricles to drain fluid and relieve hydrocephalus) reduced incidence or severity of potentially devastating neurologic effects caused by the spine's exposure to amniotic fluid, such as impaired motor function at one year of age, 40 percent of the children in the prenatal surgery group had received a shunt, compared to 83 percent of the children in the postnatal group. during pregnancy, all the fetuses in the trial had hindbrain herniation. however, at age 12 months, one-third (36 percent) of the infants in the prenatal surgery group no longer had any evidence of hindbrain herniation, compared to only 4 percent in the postnatal surgery group. further surveillance is ongoing. fetoscopic surgery