无脑畸形发生妊娠第三周和第四周之间。在这段时间内，神经管应该紧密折叠形成脑和脊髓的胎儿。

　　这个过程不能在无脑畸形的怀孕的发生，导致大脑的很大一部分的情况下，颅骨和头皮。

　　婴儿出世与无脑畸形通常是盲，聋，无意识的，无法感觉疼痛。

　　他们通常是死的但在罕见的情况下，他们可能会活得更长。

　　无脑儿发病率是一个或两个每10000人。

原文

　　WHAT IS ANENCEPHALY? RARE BRAIN CONDITION WHICH AFFECTS BABIES

　　Anencephaly occurs between the third and fourth weeks of pregnancy.

　　During that time, the neural tube is supposed to close and fold over to form the brain and spinal cord of the fetus.

　　This process fails to occur in anencephalic pregnancies, resulting in the absence of a large portion of the brain, skull and scalp.

　　Babies born with anencephaly are usually blind, deaf, unconscious and unable to feel pain.

　　They are usually stillborn but in rare cases they may survive longer.

　　The rate of anencephaly is one or two per 10,000 births.