Holoprosencephaly is a spectrum of congenital defects of forebrain development 
characterized by incomplete separation of the cerebral hemispheres. In vivo 
diagnosis can be established with prenatal brain imaging and disease severity 
correlates with extent of abnormally developed brain tissue. Advances in 
magnetic resonance imaging (MRI) over the past 25 years and their application to 
the fetus have enabled diagnosis of holoprosencephaly in utero. Here, we report 
on the prenatal diagnosis of holoprosencephaly using MRI as part of a diagnostic 
and management evaluation at a tertiary and quaternary referral center. Using an 
advanced MRI protocol and a 1.5-Tesla magnet, we show radiographic data 
diagnostic for the holoprosencephaly spectrum, including alobar, semilobar, 
lobar, middle interhemispheric, and septopreoptic variant. Accurate prenatal 
evaluation is important because the severity of imaging findings correlates with 
postnatal morbidity and mortality in holoprosencephaly. Therefore, this work has 
implications for the evaluation, diagnosis, management, and genetic counseling 
that families can receive during a pregnancy.