Objective: To determine the added value of fetal magnetic resonance imaging (MRI) when clarifying a suspected anomaly detected by mid-trimester scan.
Methods: Women attending two centers of fetal medicine between January 2017 and December 2021 were identified. The centers carried out routine mid-trimester ultrasound scans to detect fetal anomalies. Those with a suspected anomaly which required further clarification were referred for fetal magnetic resonance imaging (MRI). The medical records of all referred women were examined to determine the anomalies found at scan, MRI and termination of pregnancy or delivery. A total of 9571 women had a routine mid-trimester scan and an anomaly was either diagnosed or suspected in 449 (4.7%); an MRI examination was made in 76 cases (0.79%).
Results: MRI confirmed the presence of an abnormality in 61 referrals (80%) and failed to yield a result in one case. Outcome information was available for 69 cases: the MRI confirmation rate was 89% (48/54) in those with abnormal outcome and 40% (6/15) if the outcome was normal, P<0.0001. Among defects in the most common anatomical systems identified at ultrasound, the highest confirmation rates were for urinary tract abnormalities (94%, 15/16) and facial abnormalities (100%, 8/8). Results in other systems varied according to the specific defect but the confirmation rate was high for ventriculomegaly (86%, 6/7) and neural tube defects (83%, 5/6).
Conclusions: We have shown that in women with suspected anomaly scan results, requiring further clarification, MRI confirmed ultrasound at a high rate, particularly for urinary tract and facial anomalies.
Keywords: anomaly scan; developmental; magnetic resonance imaging; mid-trimester; prenatal diagnosis.