Long-term outcomes of fetal posterior fossa abnormalities diagnosed with fetal magnetic resonance imaging

Objective: The diagnosis of posterior fossa abnormalities (PFA) in the intrauterine period and association with pregnancy outcomes are still controversial. PFA is generally referred to maternal-fetal medicine specialists. The primary purpose of PFA diagnosis is to screen for other accompanying abnormalities, provide prognostic information to families, and discuss the termination option. Material and Methods: This retrospective study was conducted in patients diagnosed with PFA between January 2013 and September 2020 in a tertiary perinatology clinic. All patients underwent routine second-trimester ultrasound screening and definitive diagnosis was made by fetal magnetic resonance imaging (MRI) in the presence of a suspected anomaly. Results: There were 164 fetal MRIs for fetal abnormalities during the study period and 22 (13.4%) were diagnosed with a PFA on fetal MRI. Indications for fetal MRI included four (18%) with Mega Cisterna Magna, two (9.1%) with rhomboencephalosynapsis, and thirteen (59.1%) with Vermian Hypoplasia-Dandy-Walker variant. Two patients, with neural tube defects and lumbosacral neural-tube defect are still alive. However, iniencephaly was detected in last patient who died in the postnatal period. Conclusion: Diagnosis of PFA abnormalities is complex, and the prognosis in PFA is often unclear. The prognosis is not affected by maternal and fetal factors and allows the recognition of additional accompanying abnormalities. Fetal MRI is an imaging method that can provide retrospective examination and research, especially in pregnancies with poor prognoses.