Introduction: Anencephaly is one of the most common neural tube defects. Neural tube defects are birth defects that affect the tissue that grows into the spinal cord and brain. Anencephaly occurs early in the development of an unborn baby. It results when the upper part of the neural tube fails to close. Why this happens is not known. Possible causes include environmental toxins and low intake of folic acid during pregnancy. Anencephaly occurs in about 4 out of 10,000 births. The exact number is unknown, because many of these pregnancies result in miscarriage. Having one infant with this condition increases the risk of having another child with neural tube defects. Materials and Methods & Results: We report a case anencephaly fetal and his characters in this study from 11543 women in 18month attending the antenatal clinic (Taleghani gynecology center in Arak city of Iranian center). Conclusion: It is recommended for this fetal disorder, mother ultrasound at from 12 to 20 weeks of pregnancy