I think it is reasonable to believe that the cause of anencephaly could be attributed to an expectant mother's nutrition. The mother's nutrition is very important to the health of her child. For instance, women who drink during pregnancy are more likely to give birth to a child with problems. So, nutrition is very important.
It is widely supported in medicine that a deficiency in folate can cause increase ones risk for neural tube defects including anencephaly. This is supported by evidence based, peer reviewed studies highlighted in obstetric literature. This is, by far, the most important reason for women who may become pregnant or are pregnant to supplement with prenatal vitamins.
I do not think that an expectant mother's nutrition is the cause of anencephaly. While a mother's nutrition is important during the period where she is expecting, I do not think a poor diet will cause something as sever as a condition like anencephaly. I think that it is a genetic disorder.
No, I do not believe that an expectant mother's nutrition is the cause of anencephaly, because there is no evidence that scientists have tied poor nutrition to a child being born without a brain or pieces of missing brain. Poor nutrition is linked to a lot of things, but anencephaly could have lots of causes.
I do not believe that an expectant mother's nutrition is the cause of anencephaly. I think that it is either environmental or genetic or a combination of both. There was recently a large number of anencephaly cases in the United States in the same region that left doctors baffled. I don't think this is nutrition.