Purpose:
Sacrococcygeal teratomas (SCT) can be detected in ultrasonography as early as in the first trimester. Currently, prenatal ultrasonography enables a thorough examination of tumors, but it is not always sufficient. The purpose of this study was to determine the most important features of SCTs in fetal magnetic resonance imaging and to confront them with postnatal computed tomography (CT).

Case report:
Between 2009 and 2013, 5 cases of sacrococcygeal teratomas were diagnosed in our hospital using fetal magnetic resonance imaging (3 female and 2 male infants). Three of the affected newborns underwent postnatal CT before surgery. In each case, tumor size, its content, mass effect, and classification according to the Altman’s criteria were determined and compared with other features. Fetal magnetic resonance imaging (MRI) and postnatal CT were in excellent agreement with respect to tumor classification using the aformentioned criteria. MRI better characterizes tumor content and its extent compared to ultrasound, and enables a precise structural assessment of the central nervous system. Postnatal CT is complementary to fetal MRI and optional.

Conclusions:
Fetal MRI may help in the prenatal diagnosis of SCTs as it overcomes the limitations of obstetric ultrasound. Postnatal computed tomography is useful in determining tumor vascularity or calcifications, and it can depict the surrounding bone structures.