[3] Stillbirth is the most common outcome, with a few rare examples of live birth, after which death invariably occurs within a short time.

The fetal head of infants born with iniencephaly are hyperextended while the foramen magnum is enlarged and opens through the widened pedicles.

[4][5][6] Additional symptoms include:[4][7] Though the iniencephaly is not genetic with its cause unknown, studies have shown that there are certain factors that can increase the risk of mothers giving birth to children with these anomalies.

[1] Animal studies have shown that administration of the drugs vinblastine, streptonigrin, triparano, sulfonamide, tetracycline, antihistamines, and antitumor agents to pregnant mothers have resulted in offspring born with iniencephaly.

However, since maternal body habitus leads to diagnostic difficulties using this method, MRI and sonography are the most commonly used technique since there is no exposure to ionizing radiation.

[4] At the beginning of the second trimester, the central nervous system (CNS) and anatomic structures of the fetus can be clearly visualized and the characteristic malformations of iniencephaly, such as a shortened trunk, marked lordosis in the cervicothoracic vertebrae, absence or partial absence of the occipital squama, abnormal fusion of vertebrae, closed vertebral arches, formation of an encephalocele (for iniencephaly apertus), and dorsiflexion of the head in respect to the spine, can be precisely diagnosed as well as the severity and location established.

[7] Since many of the characteristics of iniencephaly, such as congenital retroflexion of the spine and fusion of the cervical vertebrae, are shared with other disorders, key differences are important to note.

[citation needed] Even though KFS does experience malformed cervical vertebra due to failure of segmentation during early fetal development, there is not retroflexion of the head as seen in iniencephaly.

[citation needed] Iniencephaly of both types carry a lethal prognosis, sometimes even ending in spontaneous abortion or stillborns.