Why is folic acid supplementation recommended for women planning to become pregnant?

Folic acid supplementation is primarily recommended for women planning to become pregnant to reduce the risk of neural tube defects in the developing fetus, specifically conditions like anencephaly and spina bifida. Anencephaly, a type of neural tube defect, is a severe malformation where the brain and skull do not develop properly, leading to significant complications or stillbirth.

Research has shown that adequate folate levels before conception and during the early stages of pregnancy can significantly lower the incidence of these defects. This is because folate plays a crucial role in DNA synthesis and cell division, processes that are vital during the early development of the neural tube.

While other options may refer to potential birth defects, they do not directly correlate with the preventative focus of folic acid as strongly as anencephaly does. Thus, the recommendation for folic acid is specifically aimed at preventing neural tube defects, making the option referring to anencephaly the correct choice.