This document discusses prenatal diagnosis of myelomeningocele (spina bifida). It describes myelomeningocele as a failure of neural tube closure, leaving an open spinal defect. Prenatal diagnosis methods include maternal serum alpha-fetoprotein screening, ultrasonography to identify characteristic signs of hydrocephalus and Chiari II malformation, magnetic resonance imaging for greater resolution, and amniocentesis to measure amniotic fluid acetylcholinesterase levels to increase diagnostic accuracy of alpha-fetoprotein levels.