BACKGROUND AND PURPOSE: Holoprosencephaly is a rare developmental brain 
abnormality with a range of severity. We describe our experience in diagnosing 
holoprosencephaly in the fetus with in utero MR imaging. We hypothesized that 
including in utero MR imaging in the diagnostic pathway will improve the 
detection of holoprosencephaly compared with ultrasonography and allow better 
assessment of the severity.
MATERIALS AND METHODS: We report on holoprosencephaly identified from 
ultrasonography and/or a diagnosis of holoprosencephaly made with in utero MR 
imaging. We compare the diagnoses made with sonography and in utero MR imaging 
in each case and compare the 2 methods of assessing the severity of 
holoprosencephaly.
RESULTS: Thirty-five fetuses are reported, including 9 in which the diagnosis of 
holoprosencephaly was made on ultrasonography but not confirmed on in utero MR 
imaging. Of the 26 cases of holoprosencephaly diagnosed on in utero MR imaging, 
12 were not recognized on ultrasonography.
CONCLUSIONS: Our results show that in utero MR imaging has a major role in 
diagnosing or refuting a diagnosis of fetal holoprosencephaly made on 
ultrasonography. In utero MR imaging also assists in grading the severity of 
fetal holoprosencephaly.