Spina bifida etiology is best described as multifactorial.

• A. Multifactorial
• B. Monogenic
• C. Chromosomal
• D. Environmental only

Answer: (A)

Spina bifida results from multiple interacting factors rather than a single cause. There isn’t one gene whose mutation explains most cases; instead, genetic susceptibility comes from a mix of variants that can increase risk, which then interacts with environmental influences to determine whether the defect develops. Key environmental factors include folate status around conception, as adequate periconceptional folic acid dramatically lowers risk, along with maternal diabetes, obesity, certain antiepileptic medications (like valproate), and maternal hyperthermia. The important idea is that genetics sets the stage and environment shapes the outcome, leading to the observed variability in who is affected and by how much risk changes with different exposures. This combination—genetic predisposition plus environmental triggers—best describes why spina bifida is multifactorial.