Incidence and Prevalence

The incidence and prevalence of neural tube defects (NTDs) varies from country to country.

Spina bifida occulta is present in about 10% of the population.

Meningomyelocele occurs in approximately 60 per 100,000 births, encephalocele in approximately 10 per 100,000 births and anencephaly in approximately 20 per 1000,000 births. (US figures).

The prevalence of NTDs has fallen as a result of several factors that include better nutrition, prenatal screening and routine prescription of folic acid in pregnancy. In addition there has been an increase in survival as a result in improvements in medical care, resulting in more adolescents and adults with meningomyelocele in the community.

The cause of NTDs is multifactorial and includes genetic and environmental influences. People with NTDs have an increased risk of having a child with a NTD. Couples who have had one child with a NTD, have a much higher risk of having a subsequently affected child. Environmental factors associated with an increased risk of NTDs include maternal exposure to certain drugs, for example antiepileptic drugs, high maternal alcohol consumption, maternal diabetes, maternal obesity, increasing maternal age and low socio-economic status.

Children with spina bifida have an increased risk of having anorectal malformations and sacral and genitourinary abnormalities.

There is a strong link between folic acid deficiency and NTDs. It has been proven that giving daily supplements of folic acid to the mother around the time of conception and for the first 12 weeks of pregnancy substantially reduces the risk of having a child with a NTD.