Can MRI improve diagnosis when ultrasound suggests a fetal brain abnormality?

Details

Ultrasonography has been a mainstay of UK antenatal screening for many years. Technical factors and physical limitations can produce suboptimal images, potentially leading to incorrect diagnoses and inaccurate counselling and prognostic information for parents. Earlier studies suggested that adding in utero magnetic resonance imaging (iuMRI) could improve diagnostic accuracy for fetal brain abnormalities. However, limitations in those studies, including the absence of an outcome reference diagnosis (ORD), made improvements difficult to assess accurately.

The researchers assessed the diagnostic impact, acceptability and cost consequences of iuMRI for fetuses with suspected brain abnormalities. This was a pragmatic, prospective, multicentre cohort study with a health economics analysis and a sociological substudy. It took place at 16 UK fetal medicine centres. Participants were pregnant women aged 16 years or older whose fetuses were at least 18 weeks' gestation and had a suspected brain abnormality detected by ultrasound. Participants underwent iuMRI, and the findings were reported to their referring fetal medicine clinician.

Pregnancy outcomes were followed up, and an ORD based on postnatal imaging or postmortem autopsy or imaging was collected when available. Developmental data were collected for surviving infants aged 2–3 years using the Bayley Scales of Infant Development and questionnaires. Information on pregnancy management before and after iuMRI informed the economic evaluation. Two surveys assessed patient acceptability, and qualitative interviews were conducted with participants and health professionals.

The primary analysis included 570 fetuses. Absolute diagnostic accuracy was 68% for ultrasonography and 93% for iuMRI, a difference of 25% (95% confidence interval [CI] 21% to 29%). The difference increased with gestational age. At 18–23 weeks, accuracy was 70% for ultrasonography and 92% for iuMRI (difference 23%, 95% CI 18% to 27%); at 24 weeks or more, it was 65% and 94%, respectively (difference 29%, 95% CI 23% to 36%).

Patient acceptability was high: at least 95% of respondents said they would have iuMRI again in a similar situation. Interviews with health professionals suggested that clinicians accepted iuMRI and found it useful as an adjunct to ultrasonography, but not a replacement. Across a range of scenarios, iuMRI added costs compared with ultrasonography alone. The additional cost was consistently less than £600 per patient, and the cost per appropriately changed management decision was always less than £3,000.

Reporting by referring clinicians could have introduced bias in diagnostic and prognostic outcomes. Follow-up rates at age 3 were lower than anticipated. The researchers concluded that iuMRI alongside ultrasonography significantly improves diagnostic accuracy and confidence in detecting fetal brain abnormalities. They recommended evaluating iuMRI for isolated microcephaly and for diagnosing fetal spine abnormalities. Longer-term follow-up of children diagnosed with fetal brain abnormalities is needed to fully assess the functional significance of the diagnoses.

The study was registered with Current Controlled Trials as ISRCTN27626961. The abstract does not specify funding and lists volume 23, number 49. It directs readers to the NIHR Journals Library website for further project information.