Complex sentence: Spina bifida meningocele and myelomeningocele is one of the most common birth defects, with a worldwide incidence of about 1 in every 1000 births, the oculta form is much more common but only rarely causes neurological symptoms.
Split into simpler sentences: Spina bifida meningocele and myelomeningocele are among the most common birth defects, with a worldwide incidence of about 1 in every 1000 births. The occulta form is much more common, but only rarely causes neurological symptoms.