Is fetal magnetic resonance imaging indicated when ultrasound isolated mild ventriculomegaly is present in pregnancies with no risk factors?

Objective: Ventriculomegaly (VM) is the most common brain anomaly in prenatal ultrasound (US) diagnosis. There is a general trend to perform fetal magnetic resonance imaging (MRI) when VM is severe (greater than 15 mm) and/or it is not isolated. The role of MRI is debated when VM is borderline (between 10 and 15 mm) and isolated. Some authors have subdivided borderline VM into mild (10 to 12 mm) and moderate (>12 to 15 mm). The aim of the study was to evaluate the role of MR in the imaging protocol of fetal cases characterized by mild isolated VM and no risk factors.

Method: As a retrospective study, 179 fetal MRI exams (mean gestational age: 26 weeks), performed for mild, isolated VM on US, were analyzed to search additional or different findings with respect to ultrasound. The potential impact of MRI results on prenatal counselling is described.

Results: In 49/179 cases, MRI and US results differed, but only in two of these cases did MRI studies provide clinically consistent additional information. In 130/179 cases, MRI confirmed US findings.

Conclusion: In this extremely selected group of fetuses with isolated, mild VM and no risk factors, MRI may not be indicated in the prenatal imaging protocol.