Question

What organ is most affected in anencephaly?

Answer 1

The Brain...

Explanation:

Derived from Greek, it basically mean "No brain inside"...

During pregnancy, the brain normally develops from the Neural Tube into the embryonic (vertebrate) brain. Towards the end of development a differentiation takes place into the Forebrain, Midbrain and Hindbrain.

Pic: (Courtesy of https://en.wikipedia.org/wiki/Cerebrum)

Although in anencephaly there can be a Total lack of brain tissue, the term usually refers to a lack of the TelEncephalon.
The Telencephalon develops into the Cerebrum, the "Main Brain".

Needless to say, the foetus has no future, and, if born at all, doesn't survive for more than a few hours, a day or two at most....