The development of the neural tube in the mammalian embryo is a tightly regulated process controlled by multiple genes that can be modulated by environmental perturbations. Etiologic factors frequently associated with neural tube defects include chromosomal abnormalities, single gene defects, maternal diabetes, and anticonvulsant drugs, although it is generally agreed that most neural tube defects are multifactorial in origin. Recent studies have suggested that the risk of having a child with neural tube defect due to a gene and/or nutrient interaction is largely preventable by periconceptional supplements with folic acid.
The pathogenetic mechanisms underlying neural tube defect risk remain poorly understood. Whereas the vast majority of neural tube defects result from a primary failure of the neural tube to properly close. About 80% of embryos surviving up to nine weeks with neural tube defects have been reported to have concurrent chromosomal abnormalities. Interestingly, trisomy has been found to be the most common chromosomal anomaly associated with neural tube defects.