Prenatal Diagnosis of Iniencephaly Apertus and Clausus in the First and Third Trimesters: Case Reports and Review of the Literature

Iniencephaly is a rare and severe neural tube defect characterized by an occipital bone defect, partial or complete absence of the cervicothoracic vertebrae, and marked hyperextension of the fetal head. Its reported incidence ranges between 0.0001% and 0.01%, with a significantly higher prevalence in female fetuses. Iniencephaly is classified into two types: iniencephaly apertus and iniencephaly clausus.As a neural tube defect, preconceptional folic acid supplementation plays a crucial role in its prevention. Early prenatal diagnosis is essential for appropriate counseling and management, particularly given that the condition is generally incompatible with life. Timely identification allows consideration of pregnancy termination, thereby reducing potential maternal morbidity and psychological burden.Herein, we present two prenatally diagnosed cases: one of iniencephaly apertus detected in the first trimester and one of iniencephaly clausus diagnosed in the third trimester.