Iniencephaly is thought to make up around 1% of all fetal abnormalities, with an incidence rate estimated at 0.1 to 10 in 10,000 deliveries.

For unknown reasons, this disease seems to occur most often in newborn females (about 90%).

Studies have shown that obesity of the mother increases the risk of neural tube disorders such as iniencephaly by 1.7 fold while severe obesity increases the risk by over 3 fold.

Agnathia (also termed hypognathous) is absence of a portion or the entirety of one or both jaws. It is a very rare condition.

Otocephaly (from the Greek words "οτο", meaning “ear”, and "κεφάλη", meaning "head") is a type of head disorder (cephalic disorder).

This is a lethal condition in which the primary feature is the total or virtual absence of the lower jaw (a developmental anomaly called agnathia). The “oto” in the name refers to the relationship of the ears to the face in this disorder.

The condition is considered lethal because of a poorly functioning airway.

In otocephaly, agnathia may occur alone or together with holoprosencephaly.

Prognosis is poor. Previous research suggested a 100% mortality rate for those with acrania. This disease is rare, occurring in 1 in 20,000 live births.

In order to better manage an acrania diagnosis, early detection is of extreme importance so that actions may be taken to help the mother and child. Families may choose either to terminate the pregnancy, or to carry the child to term. Acrania may cause a fetus to spontaneously abort before reaching term.

Little genetic counseling can be offered for acrania because the genetic origins are not fully understood. In order to make genetic counseling for families easier this disease is often differentially diagnosed with other diseases that can occur at the same time such as anencephaly and acalvaria, though these diseases may not always occur simultaneously. While this disease is tragic, reoccurrence rates are extremely low so genetic counseling is not always necessary.