ABSTRACT
Spina bifida is a developmental abnormality of the neural tube and paraxial mesoderm which produces posterior element deficiencies. The incidence of spina bifida is estimated at 3 per 1000 live births, although there is wide geographical variation. The incidence is increased in first-born children and with lower social class. It is familial. As a result of antenatal screening and folic acid supplements in pregnancy, the incidence is falling. The neural tube has completed closure by the 25th day of foetal life. The extent of myelodysplasia depends upon the timing of the pathological process. Deformities range from total failure of closure (rachischisis) to mild forms (spina bifida occulta).
