Myelomeningocele (also known as open spina bifida) is a congenital condition (birth defect) in which your child’s backbone (spine) and spinal canal don’t close before birth. It’s a type of neural tube defect (NTD). Myelomeningocele is pronounced MY-eh-lo-men-IN-go-seal. Myelomeningocele develops in a fetus during the first four weeks of pregnancy. Myelomeningocele is characterized by incomplete neural tube closure and a fluid-filled sac that protrudes from your baby’s back. The sac contains: Part of their spinal cord. Meninges (tissues covering their spinal cord). Nerves. Cerebrospinal fluid (CSF). Myelomeningocele can happen anywhere along your baby’s spinal cord. It most commonly occurs in their low back (lumbar and sacral areas).