Fetal Anomaly Diagnosis: MRI Adds Little to US


Disclosures: Dr. Gabrielli disclosed no conflicts of interest.

HAMBURG, GERMANY — Magnetic resonance imaging has a limited role when added to ultrasound in the prenatal diagnosis of fetal anomalies, results of a prospective cohort study suggested.

“Prenatal ultrasound is accurate in over 90% of cases, and MRI adds significant information in [only] a minority of cases,” lead author Dr. Sandro Gabrielli said at the 19th World Congress on Ultrasound in Obstetrics and Gynecology.

In 273 consecutive patients, MRI was performed to evaluate its accuracy compared with ultrasound in cases that were included because they were complex, because they were difficult to diagnose with ultrasound, or because ultrasound quality was poor.

Both ultrasound and MRI findings were in agreement with postnatal diagnoses in 90% of cases. Ultrasound was better than MRI in an additional 1% of cases and MRI was better in an additional 6%. Both modalities missed anomalies in 3%.

MRI was performed by expert pediatric neuroradiologists and radiologists, who were blinded to the ultrasound findings. The mean gestational age at diagnosis was 28 weeks for ultrasound and 30 weeks for MRI, at a range of 24-32 and 26-34 weeks, respectively.

“It is impossible to identify specific indications for MRI, apart from cases in which ultrasound gives suboptimal results,” said Dr. Gabrielli of the department of obstetrics and gynecology at St. Orsola University Hospital in Bologna, Italy.

Relevant additional information was provided by MRI in 2 of 126 central nervous system anomalies, 4 of 42 thoracic defects, and 2 of 35 abdominal malformations. Ultrasound provided extra information in one CNS anomaly, one thoracic defect, and one abdominal malformation. The seven cases in which both modalities failed to reveal anomalies were three cases of the rare cerebro-oculo-facio-skeletal syndrome, three CNS anomalies, and one abdominal malformation.

During a discussion of the study, audience members noted that both techniques are highly operator dependent. The ultrasound and MRI examiners in the study were all experts, responded Dr. Gabrielli, who added that results did improve over the course of the series, which ran from 2001 to 2009.

Dr. Ilan Timor-Tritsch, who also presented during the session and is director of obstetrical and gynecological ultrasound at New York University Medical Center, called for the development of teams of obstetricians interested in all aspects of fetal ultrasound and MRI to improve diagnostic accuracy. “MRI, at least in the United States, is in many, many places the replacement for a poor ultrasound.”

Next Article: