Final answer:
Folate, a B vitamin, taken as a supplement during pregnancy helps decrease the incidence of spina bifida by contributing to the healthy development of the neural tube.
Step-by-step explanation:
The supplement that decreases the incidence of spina bifida during pregnancy is folate. Folate, a B vitamin, is crucial for the healthy development of the neural tube and preventing neural tube defects, which includes spina bifida.
It's recommended by the Food and Nutrition Board of the Institute of Medicine that women who may become pregnant consume at least 400 µg/day of folate through supplements or fortified foods. This intake is essential especially during the early stages of pregnancy to reduce the risk for both the mother and the developing fetus.
Leafy green vegetables, fruits, nuts, legumes, and whole wheat are excellent sources of folate. However, supplements may be necessary to ensure adequate daily intake. Moreover, it is especially important to maintain this intake prior to conception and during the first few weeks of pregnancy when the risk of neural tube defects is highest.