This is absolutely true. Another way of saying this is: at a population based level, a very cheap and effective way to decrease the incidence of spina bifida is

This is absolutely true. Another way of saying this is: at a population based level, a very cheap and effective way to decrease the incidence of spina bifida is by providing folate supplementation. However, some mothers are genetically pre-disposed to having children with NTDs, and certain medications interfere with metabolism and can increase the risk of NTDs.